fabric manufacturers tend to follow the annual (trendy- colors) when coming up with new collections...if you want to see what is going to be coming leaf through a new fashion mag....purple has not been part of the (fashion world) for awhile...now days it is more teal/pink/brown...but it changes with the times.
you could dye some purples then try to get the interest of a fabric designer to expand your pallet :) i find that as the seasons change so do the pallets, but also lots of shops tend to carry what the owner likes, not alot of variety...there is one shop around here that carries very little in blues...i thought this was odd when i was looking and could not find a selection of blues...when asked she said...oh, i don't think much blue looks good in quilts....hmmmmmmmmm
i know there are lots of people who do love purple, seems like there would be a shop or two full of purple :)