Well, I can see that's a factor, but not necessarily an overriding one. As someone who's taught at uni myself (not pure maths) we are not usually that cynical or fond of serving up "detritus". It's not as if we lack for valuable and interesting stuff to teach if we go through foundations too quickly, and we aren't paid just for teaching. Anyway, I think most do benefit from a quite painstakingly incrementalist approach to maths; me taking that too far and sometimes getting stuck is a personal failing.
(I recall a quote by a colleague of the group theorist Simon Norton, who famously suffered a career collapse/hiatus after a series of brilliant results, something along the lines of him having opened a doorway into a wondrous realm of new mathematics, but ending up stuck there, at the doorway, obsessed by the details of the doorframe.)
If I was teaching a linear algebra course, I'm not going to say "by the way you can skip this subject entirely because it will just fall out of your working backwards through Wiles' proof of FLT". For those of us without a once-in-a-generation mind I think the traditional approach is the right one. I was only trying to say, I personally sometimes get stuck and it will be interesting to try the opposite approach.
> Frankly, professors would be more useful to me, if I could purchase their time by the hour
If you go to a good uni, at least by postgrad level you do have that kind of access, and, if you get along, you retain it for free after you leave.