There have been instances of network-enabled devices updating to put existing features behind a paywall, unilaterally changing the terms of service (can't use device anymore until you agree to new terms), and simply removing features that you paid for when you bought the device.

Why does a dishwasher need wifi?

If you're asking in earnest, the last decade has shown for profit corps know no bounds in using technology to extract, poorly protect, and often aggregate and then will make any attempt to monetize possible--often retroactively. While a dishwasher might not have much data in itself to exploit, if your internet connected TV, Car or phone which is constantly scanning for nearby WI-FI items or networks decided to start cataloguing them...well then that would just be a Tuesday for Google, Ford or Sony right?

The more data points, the worse. More breaches, more creepy facts about us floating around in some creepy company or regime's stockpile of data to be used, unilaterally against me. Or maybe the next company to buy the current company I'm happy with. Or the next regime that decides people like me aren't full humans. Between your computer and phone, most people's lives are somewhat laid bare, but add in car tracking which auto companies have stuck their funnel into during the last 5 years, add in appliances, put Wi-Fi if your shower handle...again the people adding Wi-Fi to things like a dishwasher that don't need it have only one thing to gain, monetizing your data and selling it to someone who wants to control you in some way.