Around here folks generally commute by motorcycle because they want to, and by scooter because they need to.
Motorcycle riders tend to go out in adverse weather because they enjoy the challenge, enjoy playing with their gear, or really want to use the HOV lanes by themselves.
Scooter riders tend to go out in adverse weather because their other choice is to not get to work.
This thought brought to you by the guy I saw riding his scooter in freezing rain this morning. No motorcycles were observed during my drive (in the car) to work.