It's certainly true that it would take a good bit of capital and knowledge to do a significant job of supplying plus size clothing which is as fashionable and well made as the what's now available for thinner women, but it's a little surprising that no one's managed it. I was thinking more about manufacturers than retailers-- retailers can't sell what doesn't exist.

Your wife's problem does reflect a hard constraint-- fat women will have all the variation in skeletal proportions and muscle that thin and medium build women do plus a lot of variation in fat distribution.

If you check back at the link in my previous post, there's one fat woman who says things have gotten better, in contrast to several others who say it's mostly worse.