Several reasons why most of the community uses Bolt action sniper rifles:
* First and formost it's argueably a lot easier hitting 1 shot and killing with it, than hitting one and then trying to land another one ( even with quick ROF ). So this boils down to... Semi's require more skill.. There I said it! Flame away.
* Secondly in this sh'tty community, even if you DO use a semi, and you kill anybody with it. You'll be instantly called a "noob semi user" or something similar. People really frown upon semi's and think they're the easiest thing to use just after the death modus.
* Thirdly if you CAN actually aim and your "hitting" odds are good, then there's no real reason to actually "try" semi's in the first place, just get TPG-1/PGM/ASW, hit that 1 shot and kill the enemy.
* Fourthly ( and most people who try semis don't realise this ) is if you use a Semi, you partially change roles. You start being someone who "helps" the team get kills rather than killing himself ( something like a "Support" in a MOBA game, if you please ). Because VERY often you're gonna make people 1-10HP or just simply low hp, and you're either gonna die or they're gonna retreat ( OR your teammate will kill them ). This altogether means that your ingame S/D will be less than normally.
That being said I do promote you to give them a shot if you so desire, however you simply MUST have adleast 1 "bolt-action" sniper rifle bought as well, before spending hard-earned dough on a semi. Also keep these things in mind. The fact that it actually takes MORE skill to use and on the other hand most people will call you a noob for using one regardless is what will be annoying most people the most.