No DSLRs have Removable Pentaprisms

As the title says, as far as I know, there are no DSLRs that let one
remove the pentaprism, so as to change the focusing screen. Why is that
a problem?
Well, on my web site
http://www.quadibloc.com/
I recently added a page about the history of some cameras, mainly 35mm
SLRs;
http://www.quadibloc.com/other/camint.htm
And I asked the question... why are DSLRs even a thing? After all, with
a digital sensor, you can see exactly what you're shooting on a digital
display on the back of your camera. So why bother with a moving mirror
and a heavy pentaprism?
My answer was that given the resolution of the screen was lower than
that of a ground glass finder, manual focusing would be better on a
DSLR. Plus, the focusing screen can have split-image prisms and
microprisms as aids to focusing. That was the technical reason that made
the DSLR superior.
But if the DSLR is all about the finder screen... wouldn't the ability
to change the finder screen for one's use case be important?
John Savard