Servers often don’t send player data that is outside of the immediate area of the player, but they have to for enemies that are nearby. If they walk around the corner and your client didn’t know about it, then you’ll be waiting for your ping time to even render the enemy. I.e. they walk around the corner and already shot you, then you see them suddenly appear a full players width away from the corner, and you die. Aka peekers advantage amplified.

Same deal with footstep sounds, bullet tracers, a player’s shadow, etc. Your client needs to know where all this is coming from and it can’t do that if it doesn’t know the enemy exists and where. And that is a buffer zone for hackers to derive wall hacks from.

So basically, the overwhelming majority of servers do do all those things, since the late 90’s. Hacks tend to work within those bounds. The most common, impactful and hard to detect cheats are based on providing perfect mechanical inputs. Aka aim hacks. Nothing about limiting info from the server can prevent that unless you also want the legitimate player to be unable to see their enemies.