This is exactly to the reason why PHP and before perl are successful in this space. When you extrapolate that to modern tech, you could create a shared hoster

This is exactly to the reason why PHP and before perl are successful in this space. When you extrapolate that to modern tech, you could create a shared hoster with a configured reverse proxy and per customer docker images. But that is so much expensive to build, operate and bill than an apache. And looks very close to AWS and friends.