Bra sizes after a D????

Scarlett • Have courage and be kind. Cinderella
Why are bra sizes all weird after a D??? I mean if it were numbers we wouldn't go 1,2,3,4,44,444,5 (as in A, B, C, D, DD, DDD, E). And then so many places do it differently it makes it super hard after a D. When people ask what size its like... I mean D3 in universal, most call tht DDD, some places call that size E, some call it F. 
Im currently a D4 in universal. VS labeled that an F. Most places call it E. JCPenny actually has my size, but they call it a G. Their sizes go D, DD, D(DD), G, H. Bras over a D are already hard to find, so who felt the need to make it ridiculously confusing as well??
Seriously, if you know please tell me.