Patently false. I barely hear any talk about MariaDB whereas I still consistently hear about MySQL. Please define "Everybody" in this context, because it sounds like you've conflated it with "I".
What do you mean by "ask for a MySQL database"? If I were a client, I'd be rightfully pissed off if the developer I contracted gave me a completely different database than I requested in my stack. That's a complete breach of contract, if there was indeed MySQL on the spec sheet.
Who are you working with that would flagrantly ignore the obvious differences between SQL and MariaDB?
Personally, I've never seen MariaDB used in an instance where a simple MySQL db sufficed.
