The modern Mac Pro is kind of a bizarre beast. Aside from the fact it hasn't been updated since time immemorial, it's really designed almost exclusively for high-end video editing, to the exclusion of other tasks. For nearly anything else, a high-end iMac is actually faster, not to mention massively cheaper.
This is quite a shift from earlier Mac Pros, which had wide appeal to power users of various kinds. My main computer is a 2008 Mac Pro, which wasn't cheap, but it was actually $1100 cheaper than the closest-spec Dell Dimension workstation available at the time. (In fact, Apple's price for the entire computer was only about a few dollars more than Newegg's cost, at the time, for just the two Xeon processors it contained!!!) A few upgrades over the years (RAM, SSD, and GPU) and this old beast is still lightning fast and rock solid stable.
Indeed, if you look at Mac tech forums, you'll find that an ongoing gripe from power users is the lack of any expandable machine for power users. They — we — want for the screen to be separate, space for internal storage, etc. (I love having ample drive bays in my Mac Pro.) But the problem is, most people (and businesses) don't ever upgrade computer components piecemeal. We know that they almost always replace their displays, input devices, etc, even though those could easily be kept and used with a new CPU. We power users who want modularity are simply not a large enough customer group to warrant a model just for us. (And no, the irony is not lost on me that the current Mac Pro has far, far, far narrower appeal. It seems more an engineering study than a viable product, IMHO.)