Only argument I really buy when it comes to needing bleeding edge hardware is if you're doing something like game development where it's reasonable you might be compiling, testing, and running a big IDE.

This whole "productivity increase for saving 10 minutes" is a little silly, people take breaks, get coffee use the bathroom, etc. Most folks I know doing processing heavy stuff do it all on a remote server.

With a few exceptions, I think it really comes down to people want nice toys.