Most of docker is like this. Images provided by volunteers, and not related to the project. Using docker images you don't maintain yourself, and at least don't upgrade yourself, is not the best recipe for security.
(It's pretty trivial to build your own)
This is false. The Docker Official Images team (i.e. the folks with write access to the docker-library/* organization) are Docker employees.
Honestly I don't even understand why so many docker images prefer to build software from sources, rather than just installing them from debian repositories.
Because Debian uses older relases and a lot of custom patches. One example: Nodejs still doesn't have Typescript support in the Debian packages.
Distribution packages vs. official build from source has both pros and cons.