Because re-implementing Flash is an enormous amount of work. Back when Flash was popular there were numerous attempts to reimplement it for use on Linux. None of them really got beyond the proof of concept stage.
Based on that I'm pretty skeptical that Ruffle will succeed, although I guess it does have the huge advantage that Flash is no longer a moving target and they really only have to get it to work with existing Flash movies - nobody is creating new ones.
Based on that I'm pretty skeptical that Ruffle will succeed, although I guess it does have the huge advantage that Flash is no longer a moving target and they really only have to get it to work with existing Flash movies - nobody is creating new ones.