If you're Bitnami it probably made sense to do it the image the way they did, but for everyone else, it's just a massive complication.
Personally I don't understand why anyone would have opted to use the Bitnami images for most things. They are really large and complex images and in most cases you'd probably be better of building your own images instead.
My guess is that there's a very small overlap between people who want to maintain Docker images, and the people who chose to run Bitnamis images.
These aren't just for your laptop, they're supposed to be able to run in prod
I'm still stuck with 3 bitnami charts that I keep updated by building from source, which includes also building the images, all on our private registry.
I would argue that if you run Kubernetes, then you frequently already have the resource to maintain your own images.