If only wishing made it so. I would love it if that was the case but sadly linux users running firefox, epiphany, etc are not a large base of anything and certainly not a large paying customer base....
Those sites serve Flash content to non-Linux desktops over Linux ones by a huge margin, like 99% to 1%.
And merely serving Flash doesn't mean you are an Adobe customer. The guy that writes the Flash content in Adobe Flash (in a Mac or a Windows PC) is their customer.