If nothing else, collaboration and recovery features in most common office software have only come into their own in the last 5 years or so. Earlier versions of Microsoft Office (yes, I know, but a lot of people use it) had very limited collaborative or multi-revision support, and very little in the way of auto-save or recovery post failure. It's not a major win, but it's a subtle efficiency improvement across your workforce.
On top of that, most companies had to upgrade their OS and software versions to take advantage of the x64 switch at the hardware level, since the standard install of XP was 32 bit. Now, you might argue that you don't need larger amounts of RAM if you don't upgrade the software, but that's not really true from my experience. Even with fast hardware XP would start to chug badly when you ran out of physical memory, and that could happen pretty easily as you started to run real amounts of apps. At the same time, XP was locked to some ridiculously small number of cores (maybe 2) so to get the full benefit of your shiny new 8 core machine you again have to upgrade. And all new hardware is going multi-core, since traditional speed increases have pretty much been halted by physical limitations (ok, multi-core and decreased instruction cycles, but that only gets you so far).
Again, maybe not a sea change, but things just work way faster today than they did five years ago. Remember when IE and Firefox had splash screens? We forget really easily how slow "fast" was in 2005. All of these things make workers more efficient over time, and make the business that employs them more productive.
And hell, if nothing else, companies have to upgrade eventually or people will start moving to jobs where they aren't forced to work with 20 year old software. Not everyone, sure, but being forced to work with inefficient or poorly written UIs can piss people off enough to become a legitimate factor in attrition, especially if a lot of other companies are keeping up with the tech curve.