Riding a bike in the rain sucks floppy donkey dong. Poncho or not. I've done both. A lot. Car any day over it.
While I get there are plenty of reasons to ride a bike and many arguments against it are overblown, pretending that a bike always has a solution or that that solution is always preferred is as bad as the inverse argument.
I'm not entirely sure that's what you are actually suggesting(rather I think you're just positing potential solutions), it just leans that way.