That said, if your program only feasibly runs in a shared QA/dev environment, then yes, it can be understandable to prevent devs installing random tools and utilities there. But in that case, the problem is not so much hedonistic developers, but a lack of separating portions of the code base into individually testable components. Again, you probably have larger problems than whether your devs can install their own tooling (because it's of limited use in a lot of cases anyway).
To be clear, there are good reasons for restricting certain classes of tooling. You don't want the absent minded dev installing some cloud based source code integration tool. Then again, the only way to really protect against this is to isolate the dev network, and not allow internet access. I imagine the loss in productivity is fairly great. I'm sure there's a happy (or not!) medium in there, individual to most companies.
Would you really want every developer installing their favourite tools/libs and having a complete free-for-all when you've got 200+ devs, each with their own opinions and preferences?
IT have to support this stuff, they don't want to be rebuilding the software stack every six months or so.