Right now is an exceptionally good time to be a Ruby developer. There are so many jobs that pay well and the Stripes and the Shopifys of the world are eating all the great talent up.
My guess is, that a ton of this stuff was built in the 2010s. Those Ruby developers have moved on... leaving a ton of infra behind. There's a desperate need for folks to come in and get to work on it. Most of these shops say things like, "all of our new stuff is in Elixir, but we still need to support all the old Rails stuff"
All I can say is, it's probably better than coming in to support VB... or COBOL!