Security updates.
And fixing things when they eventually break.
Honestly, there is a reason I still use a dreamhost shared plan. It's dirt cheap, been running forever, and I've never had to do the boring stuff.
And if they break my app, I can ask them to fix it.
If you deploy your app on a PaaS you still have to update everything inside the container.
Old school php hosting on a shared server does have some upsides - namely affordable support. (Sure, if I'm an extreme edge case support will not do much for me).
The same kind of thing for "self-hosting" would be cool.