At least for CS, it was pretty clear to me that PhD and post-doc is not about becoming a professor. Instead, you are getting much more interesting projects, but

At least for CS, it was pretty clear to me that PhD and post-doc is not about becoming a professor. Instead, you are getting much more interesting projects, but also a much lower salary. This is obviously not for everyone, but there are plenty of people who would like to do this for a few years (or much more -- then they end up as research scientists and non-tenure-track professors)