I used to think the same but I'm not sure about it now. We have plenty of managed backends now and they usually support Node, Python and a few other languages [1]. BEAM ones are never among them. Furthermore the deployment story now is all about docker, which is at odds with the mosts advanced features of BEAM (hot reload, but I guess few people use it.)

So, it might be the future for fully self managed web apps, but developers are moving in another direction now. That damages the mindshare.

[1] Basically the owners of those backends have a voice in which languages succeed and which not. They'll never support more than a handful of languages, because of the maintenance costs.