I've noticed that ads are absolutely everywhere, and wanted to post this to disillusion some of the places we see ads but don't realize. It would be harder to make a list of places you don't see ads.
Websites
The most common place to see ads is on nearly every website you visit. It's usually the most intrusive, especially with popups.
Books
The very end page of books and back cover of books will often advertise books written by the same author.
Billboards
Billboards along busy streets and highways often display static or moving ads. A notable mention is its role in the book Fahrenheit 451, where it was theorized that as cars get faster ads would have to be stretched out so people can see them better at high speeds.
Operating systems
Some Android operating systems, as well as Windows, show ads in a non intrusive way.
Apps
Especially mobile games, ads will be displayed anywhere possible, and sometimes used as a reward system. Social media apps display ads while scrolling, and even messaging apps will have some sort of promotion like requesting donations.
Deemed "junk mail", companies will collect and sell the address of residents in order to send useless advertisements to the residents. This can't usually be opted out of. In my opinion, this should be illegal.
Phone calls
Especially when put on hold, businesses will interject occasional advertisements in between the low quality jazz music. Customer support will also often advertise products to you while you are being assisted.
Newspapers
Newspapers have entire pages filled with ads. Some of these are promotional coupons that can be used to get overpriced products for a regular price.
Magazines
Magazines are fundamentally only used to advertise products in a passive way. The chances you actually have a meaningful experience with a magazine are slim. They are often placed in waiting rooms as a form of entertainment for people who don't want to use a phone at the time.
Music
Between songs in radio broadcasts, long ad breaks will be placed. Music streaming services will also inject ads between songs. Even the hosts of podcasts will have sponsorship segments.
Disk movies
DVD and Blueray disks will often come with ads baked in to advertise "upcoming" movies. That is, until 10 years passes and Peter Pan becomes a funny ad to see.
Movie theaters
Between movie showings, movie theaters will display long ad segments while you wait for the movie to begin. Some very long movies are even split in half, with an ad break in between for you to empty your wallet and refill your popcorn.
Bleachers
In sporting events, moving ads will be displayed under bleachers. Fun fact, these ads change depending on which channel you are watching the game from.
Commercials
Between live television, you will get 1-3 minutes of commercials and then watch the shortest segment of your actual show.
Baked into videos
Videos such as YouTube videos will have sponsorships and self-promotion baked in, causing the drastic rise of SponsorBlock.
Torrents
Some torrented files will also have text or image files attached advertising other torrenting services.
Vehicles
Buses, vans, cars, and others are often plastered with ads for different services. If you're in a car wreck, call emergency services first, not an auto repair shop.
Social media
Social media is one of the go-to methods of marketing. Besides the ads you see while doom scrolling, many pictures and videos uploaded will simply be ads for products.
Gas stations
Plastered all over gas stations, and apparently displayed on some gas pump screens, ads are placed everywhere. Is that not more of a fire hazard than eight closely packed gasoline tanks?
Posters
Pasted inside schools, workplaces, plastered on power poles and sides of buildings, posters are cheap to make and placed everywhere.
Instruction manuals
When buying a product, besides impossibly small print, some instruction manuals will have ads pasted in certain sections. Some devices like mice, keyboards, and headphones advertise proprietary software required to get the full extent of your product.
Wearables
T-Shirts, pins, bracelets, hats, and all other kinds of merch will display company names for everyone to see. Ironically, companies see these kinds of clothing as inappropriate attire on the job.
Pens
Another kind of merch, nearly every free pen has the name and contact info of businesses on it.
Redirects to downloads
Some websites will redirect you to ad websites before beginning your download. Lots of these websites (such as the infamous AdFly) are malicious and will encourage you to download malicious software.
Grocery stores
Solicitors in store, ads during checkout, product placement all throughout the store, ads over the intercom, nearly every type of ad imaginable can be found in grocery stores.
Speakers on public transport
Some subways and buses will play ads over the speakers while you travel. No napping on the bus, we want you awake to hear our ads!
Emails
Spam emails are frequently sent to people, so commonly an entire folder is dedicated to housing them. Even places you legitimately gave your email to will send you spam.
Comments and chat messages
People will often self promote their accounts on various platforms. This is a common place for scams to arise.
Solicitors
Solicitors will come on your private property just to sell their products to you. Just when you thought ads could never come knocking on your doorstep, they did.
Lawns
Lawn signs for services such as lawn care or political messages will be placed on people's property as a form of willing advertisement. Flowers look a lot better than rust and plastic.
Airplanes
Some airplanes will pull long banners with ads behind them. This is usually surrounding sporting events.
Brand names
Products produced by any company will have brand names on them. This makes it easy for advertising to flow through word-of-mouth. But seriously, where did you get that shirt from?
Search engines
Almost all search engines will display ad websites before legitimate search results
This post
Even this post had an advertisement in it that I bet most of you missed. I passively advertised "SponsorBlock" under "Baked into videos". If you missed it, that's ok. Advertising has become so common that people have become desensitized to it.