How many times have you changed databases in your production apps or are you building and selling software and wanting users to be able to pick their own database?
I don't think that is the only reason to use ORM's. They definitely help me be more productive while building apps where super-high performance is not an issue.
I really like the flexibility of being able to swap around dbs during initial development. At some point along the way once almost the whole major systems are working, I'll need to decide if I need FTS, sharding, to work on a shared host that already has MySQL / interact with a wordpress site, etc.