The weird thing is, those applications aren't "removed" when you uninstall them: http://www.neowin.net/forum/topic/1099533-advertisement-in-m...

It's just like Android, they're part of a system image. No conspiracy here. It's likely due to some intricacies of licensing Windows Store apps which I'll not get into.

Android is worse. You can't even disable in built apps, so junk like Play Magazines and Twitter sucks up RAM and CPU forever.

I can imagine disk space, but why would they be running in the background?

That hasn't been true for well over a year, probably a year and a half now. Running apps don't use CPU, default apps (now) don't often have services anyways so. yeah