I'll give the example case from my real life.
My wife and one of my best friends want to start a blog. My wife has some wordpress experience from her last job.
There isn't a big expectation for revenue, this is a hobby project.
At least when I did my 'shopping', a managed wordpress instance as far as cost, was somewhere between 'as cheap as just doing self-maintained custom solution hosted' and 'a little bit more but the extra 3-10$ a month versus my time to actually maintain it' stopped me dead in my tracks of Vibe coding an alternative.
IOW, the 'long tail' of wordpress, is the ecosystem of managed providers that exist where the user (at least as long as they are careful about plugins?) doesn't have to worry about updating the core bits, the provider takes care of that for them and can do it at a volume that makes it palatable.