The problem with all these self-hosted PaaS is that they have to reinvent the wheel. Every PaaS needs some database to store information. So what's really miss

The problem with all these self-hosted PaaS is that they have to reinvent the wheel. Every PaaS needs some database to store information. So what's really missing is that someone would build a self-hosted RDS. A complete solution with a good backup concept (e.g. wall-g for postgresql), ability to restore from backups and in later versions maybe the ability to setup read replicas and do manual failovers for high availability (because automatic is still not easy). So if there would be such a solution every PaaS could just say use "awesome free rds" for database storage and they have to implement a lot less functionality. And even if you don't want to use a PaaS and just install everything directly on a server, a DBaaS solution is still needed by a lot of folks.