I always found them more trouble than good.

They either did stuff without my permission and removed files I wanted, or they just churned my computer to a halt even when it was supposed to be idle.

They also had stupid popups that felt like malware themselves and I saw too many people fall for popups on websites designed to look like antivirus software and end up installing malware on their own computers.

I since realised I can look after my computer and it's data better than the antivirus.