You'd also have to maintain the helm chart, which is arguably far more work.
If you don't need the bitnami helm chart functionality, using more stock container images is easy and preferable.
I had not used bitnami images for.. probably 5 years at this point and they always seemed servicable in a pinch, usually used for testing and I when I brought this up recently I was also told (by k8s users) that the helm stuff is probably what actually has most people up in arms because it is very common. We're the minority who remember bitnami as a non-critical choice among many.
I would argue that if you run Kubernetes, then you frequently already have the resource to maintain your own images.