Except that MySQL is the default solution for SQL databases. When you sign up for decent web hosting, you don't get access to an 'SQL Database', you get access to a 'MySQL database'. This has nothing to do with the quality of database versus database. It's the lowest cost solution. I've heard plenty of good about PostGreSQL, and have seen it gaining some apparently well-deserved recognition. Oracle, well, I've heard plenty about the guy you have to pay to make it work right, and the scale of those numbers. But MySQL is the default, it's what your average SQL database admin is going to know if they're not in a Microsoft shop. From a business perspective, you go for your top mindshare competitor, whether or not they're the most technically mature.