Its better to have it and not need it than to not have it and then need it.
Wrong, an antivirus will eat your CPU first of all, but worst is that it will give you a false sense of security, and make you forget about the best thing to defend your PC: common sense. I work in IT and clean people's PCs as part time, what I can tell you is that the PCs that have the most viruses on their computers, are also the ones who have the most programs to defend against it... sometimes the antivirus itself is just a free version of some obscure program that qualifies at virus itself.
Once I've cleaned all the crap, I typically fix all the issues by removing the antivirus, installing AdBlock on their browser, and telling them to be careful of what they download on the internet. Then one year later they give me back the PC, and surprisingly they don't have viruses anymore.
The reality is that 99.9% people here will never get exposed to any serious threat that is worth installing more than Windows Defender - I'd even argue you should remove that one too, but it's quite technical -. Majority of people just get dumb adwares that rely on them accidentally accepting something on their browser, and ironically, antiviruses seem to be extremely poor at blocking that. And even for those 0.1% that will get something more serious like a miner/ransomware, the antivirus will ONLY protect you if 1) it has managed to detect it, which is not a given and 2) you have decided not to ignore its warning. Because ultimately that's the biggest problem, the antivirus only warns you, it still leaves you the decision, and when 90% of the warnings are false positives, people end up running the program anyway.
When I download a .exe over the internet, I always ask myself "Can I trust this?". Do you really need an antivirus to remind you that? Because that's really the only thing it does. Remember 8/61 viruses flagged it on VirusTotal, that's a 15% success rate, so if that would be a real virus, 85% of you would still get infected ... so looks to me that the only thing antiviruses have done so far is confuse everyone in the thread. Ultimately, people still wonder if they should run the program or not, no matter if their antivirus has detected it...
Crypto-mining malware for example doesn't necessarily damage your system instead it effectively takes control of its resources to mine cryptocurrency while its only obvious symptom is slower performance on your computer.
Well, you know what else eats your resources, can take away control of you and block things you wanted to execute? The antivirus program precisely. I can't tell you how many times I noticed FPS drops in game, opened task manager, to see the CPU eaten by AntiMalware Service Executable (aka Windows Defender).
/rant end
