The peacekeeper has its niche though. It beats ARs up close and beats SMGs from distance. Good players can beat ARs from far and beat SMGs up close. I would rather use any other SMG over the Vector though.
What hate? No one hates it, it's just outclassed by every other SMG except the Peacekeeper. It's the MP7 with a smaller magazine and less range. If I'm going to use a SMG, it's going to be the PDW-57 or MSMC because those can kill in three shots.
Using the same weapons all of the time gets boring. I don't care how "outclassed" people believe something to be, as good players can easily dominate with literally any gun in the game.
Also, more XP, titles, emblems, attachment and camos unlock by using each weapon. Variation = faster levels, more customization and ultimately, more knowledge and skill.
This is why Sharpshooter is one of my favorite modes. It's funny when you see someone with an SMG jumping around corners doing ok then FAL without SF comes up next and they can't get one kill with it. I swear some people don't even know what some guns are in that mode. I'll see people trying to shoot me with Executioner from so far. Or hold the trigger on the SMR and probably think the gun is broke.
This one guy in Gun Game kept getting stuck on the Executioner game after game. He'd be shooting like it was a proper pistol. So I messaged him on xbox trying to explain that the pistol was a lil baby shotgun but he was still doing it in the games after that message lol.