I've seen instances where a SP breaks something and then that user avoids it like the plague. Often that user will tell who ever will listen to avoid it at all costs as it will break their system.
They are going to get the equivalent of the SP anyway, it will just be many single patches instead.
There are also the cheaters who fear getting caught and won't update their system. IMHO they are bad news for use all. Their system is more than likely compromised one way or the other.
For Microsoft dealing with one SP instead of countless single updates makes things easier. My Windows 7 install media has SP 1 integrated into it so its no big deal for me. Its one less big download and install. It would be nice if there was a SP 2 though. I may hunt up that roll up and save it the thumb drive I have the other Windows 7 updates on. I try to install as much as possible locally instead of though Windows update. Stuff like Internet Explorer, DirectX, Silverlight, Dot Net Framework, etc.