[Mind-numbed Robot]

If it were true, a big door would open to wild theories of how the universe might work on the grandest scales, including its possible interaction with other universes or other dimensions. Even a slight difference in the speeds of light and gravity would give theorists nifty wiggle room to craft bizarre ideas about the mechanics of the unseen universe.

So why not just assume away and come up with all these other wonderful possibilities then check them for validty (even though based on possibly a false asumption)? Aren't many mathematical principles (theorems and such) assumptions which lead to seemingly valid conclusions?

[NukeMan]

Aren't many mathematical principles (theorems and such) assumptions which lead to seemingly valid conclusions?

Yes, but theorems are different than physics. Mathematicians are epistemological zealots, and aren't supposed to use 'observations' to prove or disprove a theorem, but only the axioms and logical, non-contradictory application of identities afterwards. Unless, of course, you are Luitzen Brouwer and others like him, who don't accept the law of the excluded middle!