I'm not arguing against dedicated servers or a solid PC version. Of course we would all want that. I'm just giving your my opinion as to why they decided against it.
I disagree that this will hurt their sales. CoD4 had a record number of piracy for the PC version, and there are a lot of people that will now buy a console version instead of pirating a PC version. They also saved millions of dollars in development by spending a short period of time porting to the PC without adding new features.
In the end, MW2 is a console game. So if you want to play then get a console or just wait for the next PC specific FPS. Although, they all seem to be turning into console games.
