There's also a very good reason to not move some things to alpine, including ruby and node applications. A significant number of ruby and nodejs apps depend on some c/c++ code hidden away in this module or that gem. Any time you're compiling c/c++ code, you run into a chance of musl vs libc causing differences.

These differences can range from building requiring different options to the application having strange performance characteristics to random crashes (rare!).

In addition, people who write these modules typically test against an ubuntu or debian system, so those are much safer bets. Alpine makes no serious attempt to match packages with those, either in breadth nor version.

It really isn't feasible to unilaterally move people, and for compatibility reasons Docker does not often change tags in such a drastic way.

The official docker images are often offering alpine alternatives in different tags, which is not the same as "moving towards" as you remarked.