getting a cold isnt going to turn you into a botnet or steal your banking information or encrypt your house and hold it for ransom.

Actually, yes, it kinda is. If you catch a virus, it basically uses your body as a host to produce more of itself to send out and infect others with, just like a botnet. And I'm no medical expert but I'm sure you could find a similar equivalency for the other example. There's a reason the term "virus" was adopted into computer science, because certain software can exhibit much of the same behavior as the real life thing. It's just art imitating life, that's all.

If you want a bodily example, Its like wearing a condom when you have random sex with strangers. Unless you are looking to catch something horrific, you use protection, every time, all the time.

Even then you might end up choosing not to use one, if you do end up meeting that special someone and get them tested for STIs.