Funny thing about Postgres
The power of marketing: psql has always been ahead of mysql in features and standards support - previous to mysql 5 I'd say the lead on features & standards was significant.
I do not mean to say mysql was crap, it was quite good enough for web apps which creators valued speed above all. They did not think they needed relational integrity in addition to speed, and it seems many web programmers used to thing a join was better done in the scripting language using multiple dbms queries. Psql always provided SQL compliance far in excess of mysql.
Yet mysql had better mindshare - I suspect it tied into the 'my' thing: My Computer, My Documents, My Pictures, MySQL. Mine mine mine, so self affirming. Whereas 'postgre', what that?