Obviously the main argument to this is why should they have to in the first place on an older product. There are many very good answers, here's three:

One: because they can, it's a simple two or three page script.

Two: many of their competitors continue to support their remotes, thus its good for business and their image. (customer loyalty!)

Three: because the OS systems they were designed to be used with aren't even being offered by some of the biggest computer companies in the world (Dell for one).

Not going to attempt to tackle MS on this one...we all know vista, where would we start??!