My experience is the work in academia is more interesting and intellectually stimulating than my high paying tech jobs. That would be one motivation to go the academia route instead of the tech route.

If you come out the other end of a PhD, then you have the opportunity for best of both worlds: high paying job to work on the problems you find intellectually stimulating.

Also, it is cliche, but doing a PhD does train a person in a way to think that you don't necessarily pick up in a normal job.