I've asked this same question at SkyWest... we use those dumb bridge adapters which lets all the wind/snow/rain in even at jet bridges with the RJ adapter built right in. It seems like the airline and the stations don't like training how to use it because of the possibility of damaging the airplane (such as the pitot tubes/stairs) with the jet bridge or canopy.

I'm not too sure how much truth there is to that. We use it at Omaha on the United side, and it works really well. I'm waiting for someone to slip and fall in a slippery jetway and sue... then I'm sure we'll be using them as much as possible. I nearly ate it in a slippery jetway in Columbus the other morning.