There's a kind of backwards justification going on here, where since Monday the Mac Pro is defined by what Hollywood video editors need. The only reason they are the focus all of a sudden is because Apple started with a price for the new Mac Pro, and worked backwards from there.
In my example, I was taking it to an extreme. If Apple had decided the MP needed to cost $200m and be a supercomputer, everyone would now be running around saying it makes total sense because "that's what it costs to provide meteorologists with the tools they need". It may well do, but why should anyone else care? A much larger number of people just want a powerful Mac tower that doesn't cost two legs and a spleen. Doesn't seem like too much to ask.
I am not sure what kind of audience the Mac Pro (or the Power Mac) was intended to back in the day. But I suspect it was bought by many prosumers and enthusiasts, just like the MacBook Pro (and the Power Book before it).
Now, the Mac Pro is far more expensive, and it does not seem to really make sense except for enterprises that need very powerful workstations. The iMac and the iMac Pro seem already more than adequate to address the needs of prosumers and enthusiasts (except for the expandability). Apple seems to have made the only expandable Mac very expensive on purpose, to take it out of the reach of the average consumer.