The second is why one would reduce the natural
rythm of any piece of music to a regular beat.

The whole genre of Hip Hop has used this to adapt music into a new form

A drummer
or percussionist worth the name can add beats
to whatever is thrown at him, regular or not.

Not everyone works with live drummers. And a tool to either even the tempo or create a tempo map of a piece would help re samplers extend on other musical ideas.

What would you think if someone were asking
'is there any program that can simplify the
harmony of a song so I can play a three-note
bass line to it' ??

If the piece is under a free license or public domain. I would say "great!"

Now, I am an accomplished drummer and don't create music that would require this. However, I have no qualms with anyone creating art in whatever way they see fit. So, instead of criticism a simple I don't know of a tool that does that or silence would do.