Splash_King
The Scrubbiest of Hunters
But anyway, yeah, the in-game sound effects are a VERY important tool! Try playing a whole game on mute - totally different experience, although I find I sometimes focus more when I do this...hmmm.
Yep, there're benefits to competitively playin' games either on mute or with higher sound details. The best part of playing on mute is as you said; you'll have a more intensive focus. If you lose one sense (hearing, in this case) your other senses sharpen. Since you have less information to take in with noise out of the picture, you'll notice more subtleties and process info quicker as a whole. Unfortunately, some games just can't be played without sound since you might absolutely need audio cues... Or it might just kill the enjoyment.
That, or the benefits of elevated sound like ya detailed are just-plain superior to the perks of silence.