Why does it seem when a new COD comes out pc users need a upgrade?

This is a simple to answer question that seems to make me mad as well. First of all they are trying to keep up with the other shooter's graphics. A lot of PC gamers want to have higher graphics then the console players so they make sure you have to update. They are trying to keep with games like Battlefield 3 coming out on the Frost byte engine which looks like it is going to look amazing. Without an update there would be a lot of complaints and they could not win the shooter war. The reason they are going on the path of steam is due to the fact that they truly would rather have non dedicated servers which means less cracked servers making it harder for pirates to play online. I admit I loved the days of dedicated servers on the COD series and that is why they brought them back on COD:BO. I hated the servers in MW2 so I use AlterIW Net servers because they are dedicated and have mods and admins.