The actual stalking aspect of sniping could be considered more difficult than real world sniping for the simple fact you have to get that much closer to the enemy to hit them. Within hearing range, never mind visual range. It's not like you're tagging a dude from 1000+ meters, you're tagging him from, in most cases, 100 meters.
It's hard to sneak up on someone that close. Unless you're a ninja... Then you've got it made.