I've been accused of cheating many many times, despite never cheating. I was blacklisted from a community counterstrike server back in 2002 or so for "cheating" after a lucky couple games where I got a LOT of headshots with guns that aren't very good accuracy wise. I was playing with very good players, and even some of them thought I was running cheats.
My experience says people vastly underestimate how far a good lucky streak and adequate reaction time + aim can take someone. Plenty of friends have similar experiences of being accused of cheating when they play well.
It probably doesn't help that the asynchronous client-server model of fast paced FPS games introduces weird effects with respect to latency. (I.e. rewriting history to show some high-latency player killed you after you've already observed visual/audio effects for their own death.)
Though I've heard now it's possible to load your USB peripherals with cheating software.
https://hackaday.com/2017/07/29/injecting-code-into-mouse-fi...
Second, what kinds of cheats would you expect using peripherals? Any visual cheats would likely be detected, since player's screens are often viewed by referees and/or televised. I suppose an audio based cheat is conceivable. The screen and the audio are the only output from most computer games.
Aimbots these days look almost indistinguishable from good playing. The point isn't to be perfect. It's to give some kind of competitive edge. If you can take even 15% of the effort away then you can focus on other things.
Also game streaming is big now and being "good" attracts more viewers so there is also a lot of money to be made by cheating.
I have completely stopped taking video games seriously in any capacity as I am pretty confident the entire culture of competitive gaming is completely infested with cheating.