Lots of nice games to keep alive.

Video playback can be done via WebGL shaders, just like rendering video on the good old days with SIMD.

And most important, why not?

Someone will eventually do it, there are already JVM and CLR ongoing ports.

There is even an ActionScript to Javascript __piler https://as3js.org/

ActionScript is really the easy part of making a Flash player: the hard part is being bug-compatible with almost every version of Flash ever shipped (the Adobe implementation has lots of branches depending on version of Flash that created the file!).

That, as far as I'm aware, is why Shumway died.

Archival purposes of old flash videos? It would be sad if it would become impossible to watch those old pieces of Internet culture unless someone had exported them to an mp4 video file.

Same with games, for which there isn't even an alternative format to save them in.

There is still nothing better for (online cartoon) animation.