I completely support this. I write a
ton of open-source software, and have many published packages.
Each one that I publish is a Responsibility. Like a parent that has children, the package is no longer “completely mine.” All changes and fixes are made, keeping in mind that someone may be dependent upon my work.
I’ve been writing SDKs -literally- my entire career (I can link to my very first engineering project, in 1987, where I designed a hardware system, and a companion SDK).
A perfectly legitimate reason for keeping code private, is that I am not willing to support it for any use, other than my own personal use.