I've been playing CS GO for a couple of weeks and prior to that I've never played this type of FPS game so I'm not very knowledgeable in combat skills. I've been playing Deathmatch from the start in order to get better and I constantly see other players crouch right before they shoot me. I'm getting better at headshot-ing people, but sometimes i'll round a corner, lock eyes with an enemy, and try to kill them but instead end up missing because they crouch and shoot at me (mind you, I know pros do it when they have no other option of dodging enemy fire, but these other players do it all the time). It's annoying when i'm playing normally with other players then out-of-the-blue I meet one of these people.

Is this a thing that only noobs do? I'm not sure since I mostly play Deathmatch when most experience players play competitive or other game modes.