Why not always rolling release?

I'm hoping someone can explain some things to me about the way the distro-makers operate. I'm a bit confused as to why they do things the way they do. So as we all know, Micro$oft practices rolling release. They release a particular OS, then they just release service packs and updates for it for 7 years. Well now I think they've said they're going to lower that to 5 or something, but you get the idea. For a good long time, you're going to see just the same OS, with any major changes needed, being done in the form of downloadable updates.

Now I know that some distros do this, but most don't. IIRC Arch and Manjaro do rolling release. This appeals to me, because as a very new linux convert, it just fits in with what I'm used to. So why doesn't Ubuntu, or Mint, or all the other distros, do this as well? I mean I know that like Microsoft, yeah they'd eventually need to just release a full new OS. Or would they? If linux is so modular, and can just be gutted and rebuilt on the same install, why don't they just do "service packs" or something like M$ does? What is the point in releasing a new version of the OS every 2 or 3 years? Why not just wait a lot longer, and just do updates?

The way it was explained to me, even major changes to the OS could actually be done without having to reinstall it or wipe the drive or anything like that. Why do some distros do rolling release, and not the way Ubuntu does it?

Also, another related question. When the next big Ubuntu comes out that you want to install, and you go to install it, will it be like going from XP to Windows 7? Do you have to pretty much wipe the old OS off, and install the new one? Or is it just like some kind of major upgrade, and you don't have to move everything you want to keep, off of that hard drive in order to do the install? I just find it all a bit confusing.