If you are building for mobile then it doesn’t makes sense to run CI/CD on the Pi and if you are targeting your own bespoke edge then likely having dev boards which can represent your edge hardware more accurately is probably going to be a better way.
Running CI/CD for ARMLinux apps is pretty much the only use case I can think of and even that might be limited if you are using extensions.
I don't understand what point you tried to make. These hosting services, and also clients, are quite intentionally targetting the raspberry pi. More specifically, they do target Debian running on Raspberry Pi. I don't understand the confusion. I mean, is it also hard to understand why AWS users pay for ARM instances running Amazon's custom linux distro? In both the Pi and Graviton you can run nginx, nodejs, Python, ssh... So, what's the problem again?
A considerable amount of people is already assembling and running clusters of raspberry pis, including hosting companies. A cursory search through eBay or Amazon can provide you with an idea of how many people are already operating these small clusters and spending money on this sort of setup. I'm sure there's a significant demand for a COTS cluster solution that allows people to avoid having to MacGyver their own cluster just to get Docker Swarm or Kubernetes running on a small cluster of raspberry pis.