Sniping in CoD, Halo, Quake, TF2, Counter-Strike, and pretty much all games that use hitscan rifles is incredibly easy to do. It's not that easy to get a hang of, but when you're good, you are one of the closest things to unstoppable there is. One-shot kills at all ranges is something to fear if the sniper you're facing off is incredibly aware and has golden aim.
It's different in Battlefield because the sniper rifles aren't hitscan weapons, they fire projectiles - granted, they fire extremely fast moving projectiles, but aiming at far distances is hard. It's a lot of movement prediction, a lot of guessing the mil bars and chevrons on your scopes, a lot of scope sway compensation, and of course that freaking suppression. A sniper that can't take out an enemy in less than a second from one hundred meters away is going to die or get horribly suppressed; from around three hundred meters away, they're going to get horribly suppressed; and any further, the enemy is surely fucked but it is hard to hit a moving enemy when you are pointing your scope one mil bar in front and two mil bars above them and just barely missing them. It's hard because you have to relearn weapons.
Another problem with Battlefield is that there is no real way to practice for hitting long distance enemies other than pubbing it up as Recon. There's no level in the campaign that has you engaging enemies over one hundred meters away, and there's no form of practice mode to help you.
Also, the sniper rifles in Battlefield 4 are just freaking weird. You have no idea where a bullet lands because of vapor trails, netgraphing had shining moments of watching a bullet fly through an enemy's head while doing no damage, the only snipers given were ones with low bullet velocities, and some of the attachments that help with sniping like Straight Bolt Pull wasn't available in the beta.