It COULD be a good tool and there are web based database management tools that ARE good. Not sure why phpmyadmin is still popular.
I guess its just all the tutorials for people who shouldn't be in the database in the first place. Things like changing site url, reseting admin password in wordpress. Every tutorial is always the same, not really teaching any concepts just copy and paste and click here and it will work, so its useless without phpmyadmin.
I bet If a hosting provider offers a good alternative, people will complain because they cant get their 2 braincells to figure out the different interface.