I'd argue more people use Elixir over Erlang at this point. Sure its just an abstraction on top of Erlang, but people learn through Elixir nowadays, not through Erlang.

If you want to learn the actual mind changing aspects of the BEAM, clearly learning the simpler, smaller language with a more direct route to the juice is the way to go. Hence Erlang, not Elixir. I learned Elixir first back in 2015, and then learned Erlang, and have had the pleasure of using both in production. When all was said and done I really think Erlang was better, especially over a long enough time frame.

As a general point I'd like to state that I don't think it really matters what "people" do when you're learning for yourself. In the grand scheme of things approximately no one uses the BEAM, but this doesn't mean that learning how to use it is somehow pointless.