As a level 10, I only did it because it was there. I did stop on Level 6 so I could get my gold Dragunov, and then I carried on. I did it for the challenge, not for bragging rights. Only thing is, people assume that I'm absolutely awesome, when really it's just perseverance. Amongst my friends on COD4 Lvl 10/55 is the norm, but I judge people by their K/D in game, and their win streak. I don't protect my stats by pulling the plug, but some of my mates do.
On R2 couldn't give a monkey's, I only play co-op and campaign.
In answer to the Question, its only for personal gratification that I look, otherwise I'm not really fussed.