A PhD is a license to do deep research. Deep research careers are very rare, but for the right kind of person, they're great. However, deep research by definition means it probably won't work, and there's just a lot more money in doing things that will probably work vs things that probably won't. So it helps to be extremely talented at deep research if you want to pursue the PhD. Also, most engineering PhD's are bogu…
The first was a researcher who talked to us a few times (just a few hours of meetings) then returned a few months later with a pile of MatLab code and a "problem solved!" attitude -- his simulations showed that things were working great. We looked at the code and while it taught us some things, it was obviously not shippable. None of his stuff wound up in the product, though it did point us down some interesting paths (some good, some bad).
Another researcher got a desk smack in the middle of the product team and spent 18 months sitting with us full-time, porting and dramatically improving his algorithms. I'd say that he learned just as much from us as we learned from him. His first few months were rocky, but he eventually became a productive and supportive member of the team. I hope that MSR treated him well upon his return.
Personally I think that research is great, but it's fantastic if you can occasionally ship your work to real customers.