If serverless were easier, more people would be using it. But it's not simple or straightforward. You have to learn new systems and conventions, it has a bunch of weird considerations depending on the use case, and most people just use it when they don't want to figure out what instance to run some periodic, one-off job on.

It's a niche, just like all solutions that aren't a single Unix process on a single Unix box. Even CGI scripts are a niche. You pick the niche that you know.