Well they are OP they don't get penalized for mistakes unlike other weapons. For example if you shoot to earlier with a shotgun or to late your going more then likely going to destroyed of course if you react fast enough you coils escape. Primaries punish you based on range and head shots lastly heavy punish you through limited ammo, every shot counts. Also fusion punish you for charging to late or earlier snipers don't have anything like this.

And they do get penalized, if you miss a shot with a 1k often you will get out sniped or done in by a scout rifle

But that's versus another sniper which makes sense since your both using OP weapons also considering the damage versus RoF on a sniper you usually end up beating the Scout. My friends do it, I've done it the few times I've used a sniper and I've seen it happen.