I originally was using MySQL to learn with rails because it was so simple to set up on my Mac.
The only reason I migrated (quite early I may add) is that at the time Heroku pretty much mandated I move to postgres.
I'm glad I made the move, but I'd say awareness of the alternatives is the limiting factor. The brand awareness MySQL has is pretty big compared with many others. I wonder how much impact Heroku's decision to support postgres has helped those similar to myself drop mysql.
The only reason I migrated (quite early I may add) is that at the time Heroku pretty much mandated I move to postgres.
I'm glad I made the move, but I'd say awareness of the alternatives is the limiting factor. The brand awareness MySQL has is pretty big compared with many others. I wonder how much impact Heroku's decision to support postgres has helped those similar to myself drop mysql.