The Knowledge Base article on "why we don't have SRPMs" says:

"We are currently investigating using a source RPM generator as documented via a macro."

< https://mariadb.com/kb/en/mariadb/documentation/getting-started/binary-packages/rpm/why-do-mariadb-rpms-not-include-the-source-rpm-srpms/ >

I couldn't find any related Jira issue though, thus I've now submitted this one.

Reason for this is that I'm missing the ability to say

  yum-builddep MariaDB-server

to pull in all build dependencies required to compile MySQL from source.
I don't even plan to build from SRPMs, but being able to install all required packages in a single step is pretty convenient even when building from source tarballs or directly from bzr / git ...