People were still implementing new, paper-based workflows in 2000. By 2004-2005 that had mostly gone away, but jumping from NT4 to 2000 meant jumping 25-40% of the office to a new version, typically the smarter and higher earners who deal with change fairly well.
By 2005-2006 you're looking at Vista era and half a decade of XP dominance, nowadays all employees not working in food service and/or retail are assigned a desktop. This resulted in a huge upswing of PC sales which has now leveled off. So now in addition to server class hardware and A-level users, you're also having to migrate your B, and in most cases C, D, and E-level users at the same time. Even the guy in the mail room needs a PC to check email from his boss and HR once a day. Our copy room has a desktop to open word files.