I have always said the same thing lol
I believe they include that for people that don't know any better. To someone fresh in the hosting industry that long list, and the fact theat they may not know that Flash is not a feature hosts offer, this may determine whether they or some other host gets the sale.
Although Flash is streaming technology, it most certainly is not necessary to stream anything in Flash. As a matter of fact, most flash animations use absolutely no streaming whatsoever, just vector or raster images.
So, primarily, including Flash as a feature on your hosting spec list is either to lengthen the list or persuade newbies into buying.