I feel that is purely a tactical choice,tactical for in-game ofc.
It's pretty obvious as for the reasons but we know about it or even do it?

Here http://www.brinkthegame.com/community/blogs/detail/?id=6 under the title Making Movement Sound Good says that :

Also,chatting with some hardcoe PC players revealed a little secret: when playing online matches on the PC,they would disable all ambient sounds so they could hear the footsteps of their enemies.

This doesn't mean that we must be hardcoe players to do it,it's an obvious factionality,but some may say "i don't hear anything than gunfire" or something else.

If you keep reading you'll see that there is detail in this department of the game also.So,possibly will help...

In that article, he talks about how if you need to turn off ambient sounds to hear other sounds, then something is wrong. In Brink, he made it so players really don't need to compromise one thing for the other, in terms of sound.

If I had a good pair of headsets I would, but mine is just the little earpiece thing with the microphone attached to it.

I don't like the corrections they make to posts...

Thanks for the notice...guess english not my native doesn't help.

I'll rephrase then: Do you use this option in FPS genre?Apart that Brink that is...

I see what you did there....