Air Shocks or Air Bags on TT

I would expect they would be commonly in use but they aren't.

I'm sure it has to do with cost more than anything else. Most trailers (caravans they are called down under) from Australia have this feature and there are three or four aftermarket companies that will convert your leaf springs to air. YouTube is full of videos on it. But at $4K to $6K it is too expensive for a simple $30K travel trailer...