Sniping isn't something to diss. Sometimes a decent sniper can be the lynchpin to victory.
The problem is that sniping is hard to pull off in most games to the newcomer, who would then shun the sniper as someone who is a cheapskate, not able to 'play the game proper'. However, who is the guy who covers your ass as your run down the street, moving from cover under fire?
Notice how, when a sniper comes into a game, he is usually the quickest to be eliminated? This is because he strikes hard and fast, can move with stealth, and can be devastating when used properly. Not only that, but it takes a cool head and steady hands to snipe. Its not a spray-n-pray role - you must be deadly accurate, literally.
People groan when Wastelands or Derail comes into play, because it is sniper heaven. This is because those people don't understand the proper way to play these maps. You must use stealth, keep a low profile, blend in with your surroundings. It shouldn't be about getting the highest score - it should be able feeling the thrill of lying prone for a few minutes, waiting for your opponent to slip up - and punishing him for it with extreme prejudice.
People say snipers are campers, associating 'camping' with 'dog turd'. But, again, these are the type of people who run around wildly, not checking their surroundings, making noise like a wild rhino in a glass warehouse, expecting people to rush into their sights. This is not how you would fight in the Real World, why do you do this in a game? Because it is fun to rush blindly in as a hero - and the sniper is there to put you in your place.
Btw, bunnyhopping in MW2? Just a better headshot challenge.