I guess one of the issues is that there is little incentive to use anything else other than sniper rifles/marksman rifles (if such thing exists). AI doesn't suffer from supression, so a machinegun becomes inferior (unless you prefer the high capacity). Another possible candidate would be a rifle with a grenade launcher, but to use that it requires some skill (motion prediction, correctly estimating distances, finding cover from where you won't get killed) that the current sniper rifles do not require (estimate range, even if using bullets, adjust zero, aim and shoot). The other issue is that on some servers there is an issue with the AI engaging you effectively (probably caused by what I perceive as low skill level of the players), and you end up with: select sniper rifle, engage from as far as possible from where you can see the enemy (which happens to be fairly close, because anything really far would require people to be patient, predict the motion of their targets).
Less than sniping is cool, more like it's just the best tool for the job since the environment/game mechanics don't really make the other tools better. To put an example: in dslyecxi's videos, when bullets start firing, everyone immediately runs to cover/concealment and/or goes prone. LMGs start firing. Grenades may be thrown/launched. Both sides do this (unless they are playing the AI, and I won't really talk about how the AI behaves in this case). On the public servers? The AI doesn't really try to find cover. And I perceive that the general player population doesn't know how to do it effectively.
Just my two cents.