Because it is not just laggy, its unplayable more than the time, when you spend a half hour trying to find a playable match because most of the ones you try to join either, A:lag out and die, B:are so laggy you cant play, or C: are FILLED with unkickable hackers. besides, it kinda randomly chooses the host, and most people dont have good connections. its a broken system.
I agree entirely with A,B, & C. This angered my to no end after 2 months when the frequency of these items increased about 10 fold. I solved my problem by these steps.
A. Uninstall MW2
B. Install Bad Company 2
C. Enjoy dedicated servers, low pings, and VERY few hackers that normally get banned if the server has a good admin.