It's shocking that this is even still a thing despite common sense debunking the theory that common sense is the only anti-virus you need in a world where you get virus from things completely out of your control
Because it's still a thing. It's actually a pretty common thing too. It shouldn't be a thing. Common sense helps, but that's it. You can avoid a lot of problems by having common sense, but thinking you can avoid all of life's problems with just common sense alone is extremely stupid, and virtual problems are no different
Computers are fast enough that having an antivirus in the background somewhere is essentially costless in terms of resources. No sensible person says no to a free insurance policy.
It's not costless when the stupid AV's restrict the functionality of completely legitimate programs because it mistakenly assesses them as a danger.
Sure, completely disconnect your computer from internet, never install any programs, don't trust other people's flash drives, and live in solitude...and you'll never need an Antivirus.
Anything else...Well, if you're going out of your way to live a "Virus free internet lifestyle", you're seriously going through more trouble and inconveniencing yourself far more than just installing a damn A/V program ever would.
It's like saying you keep your money in your mattress because you don't trust banks. The day your house burns down or gets broken into the rest of us will laugh. And you, you'll be left regretting having dedicated your time to not allowing open flames in your house and making sure your burglar bars were always locked.