I've recently worked for a large bank still running XP and IE6 and their migration policy stipulated that upgrades to the OS weren't considered until a SP has been released; perhaps this is more widespread, and enterprise applications notwithstanding, the insignificance of the Win7 updates could be in anticipation of IE9...
If they are still running XP and IE6, I suspect some other problem exists, like a very critical program that was done in, say, Webclasses or plain ASP/VBScript, that breaks under IE7 and nobody dares to touch it for it will collapse.
Think of it... All previous MS OSes really became feasible after SP1 and started to shine after SP2.
Win 7 seems to be a notable exception (truthfully it is a Vista SP2). Anyways one supper happy Win7 user here - although 64 bit is STILL not what it should be - Firefox memory leaks are a bit worse and it is noticeably slower (I have 32bit W7 on laptop) plus some other minor issues - but that is hardly Microsoft's fault.
