What is the science behind why we like to make musical phrases in an even numbers of measures?

I don't think I've ever heard a song where there's an odd number of measures in a phrase. If there were such a song, I would probably expect it to be in 3/4 or something similar.

Along the same lines, why are all the measures in a phrase (usually) multiples of 4? It's not very common to have a 6 measure phrase. Usually it's something like 4 or 8 and sometimes 12.