Because String Theory is way out there in terms of speculation. Instinct tells me it doesn't come close to accurately explaining or describing the fundamental nature of reality, if such a single explanation of reality even exists. ie, there is a near-infinite number of perspectives in which to view or experience the universe. In other words, from the perspective of something residing in the realm of quantum mechanics, its experience is completely different than something in the macroscopic/everyday world. How can we possibly select one of these countless possibilities and decide that it is the correct and only perspective in which to describe the universe.
I thought much of the quantum infinities had been excluded by pegging values to those twenty odd fundamental numbers. Weight of a proton, etc. meaning, the possible universes were few.
but Im certainly no expert. I find the non Euclidean geometry and higher dimensional studies fascinating.