When talking about odd time signatures, people always talk about dividing the time signature into beat groupings, and those beat groupings are most prominently 2 and 3 (for example: 5/4 being 2+3 or 3+2). Why aren't there other beat groupings such as 1, 4, 5 and so on ( n>3 not being divided by 2 and/or 3, meaning that 5/4 can also be 2+1+2, 4+1, 5, and meaning that 2+2+1 =/= 4+1)?
So - if there aren't other beat groupings, could you explain why (proof), and if there are, could you give examples of cultures and maybe even pieces which use such beat groupings?