The problem with that logic is most users aren't even capable of knowing if they have been compromised. Your computer not shoving popups down your throat or running poorly doesn't mean it's uncompromised these days.No. If my Win 7 installs ever get compromised, I'll come here and personally apologize. Till then, from my cold, dead hands...
Attacks have become much more sophisticated over the years and threat actors more clever. They know your PC will drop from their botnet if a user notices unusual behavior. I've even heard of some attacks that will patch's PCs behind them to keep out competing "hackers".
Unless you're monitoring all traffic in and out of your PC \ network you really can't be sure. (And maybe you are, I see plenty of users here capable of doing it. I'm just say the majority of users can't \ don't.)