Conventional bicycles are bulkier than these other solutions, making them harder to carry onto whatever mass transit one is using. On Caltrain, for example, bicycles are restricted to a special car at one end of the train. On other systems like BART, bicycles aren't even allowed on many trains.

The other problem with conventional bicycles is that it's hard to go very far without getting sweaty -- depending on the weather, of course, and one's patience for riding slowly. It's nice to have power assist.

Folding bicycles can be compact enough to carry on any mass transit conveyance. The Metroboard is certainly quite compact and portable. Not sure about the Trikke.

You're right that weather can be a problem.