Because it requires an entire JVM of baggage, is terribly complicated and doesn't really give any benefits over anything else.

Its like a Swiss army knife with a million blunt obscure tools rather than 5 useful sharp ones, or a crazy girlfriend who has three violent ex husbands who keep coming round to your house and lives with a crackhead.

Go is a trip to your Volvo dealer - uneventful but you get what you want at the end of the day and get where you want to go and when you're done, you're done.