A lot of businesses I talk to have a lot of legacy applications which work well under XP, but break for whatever esoteric reason (for example, an old Access database, or VB6 app) under Windows 7/8. An equally large pain the ass is a
ton of intranet sites break when switching to IE9 and above (heck, a lot of companies still force IE6/7 and below with Group Policy). It's difficult to make a case to management when everything is working well (it's hard to explain the nuances of "end of support life cycle" to someone who needs help "getting to the Google").
Also, there are a fair number of desktop software products which don't even support Windows 8 yet. Hard as it may seem for the crowd here, most of the software world is not on the HTML5/Ruby/OMGMVCJAVASCRIPTBRO bandwagon yet.