SQL is fantastic for relational data - it maps pretty closely to relational algebra.
About all I'd change is placing the column names after the table/object names - "FROM table1 SELECT col1, col2" instead of "SELECT col1, col2 FROM table" because it makes code assist features easier. (Microsoft did this with LINQ)
SQL makes sense, but at its core, it's a query language, not a programming language. You can do lots of arbitrary computation with it if you want and use it for things it's not good at, but for its intended purpose, it works pretty well.
1) He didn't say "implementing it" is simple. Just that the language (using it, getting started with it) is simple.
2) Vendors get a lot of benefits by NOT providing a standard implementation (lock-in, for one).
3) It's not like everybody runs around implementing every new standard that comes out. Vendors have their own timelines and priorities. Heck, we've waited how many years for CSS3 to be implemented? (and it's still missing full support...).