Rubber gas lines okay?

I recently read an article in RV magazine about replacing a refrigerator in a motor home and was surprised to see that the gas supply lines were rubber with factory crimped fittings going into a black pipe manifold system in the motor home "basement". All I have seen in trailers are copper lines and flared fittings other than at the tank to regulator lines . Are the rubber lines ok for the final hookup instead of copper? Sure would make replacing my next appliance easier.