> 1. They're harder to drive.
This is pretty subjective, but I disagree. There are some ways in which they're slightly more difficult (e.g., a manual transmission) but that's an incredibly minor additional challenge. On the other hand, on narrow city streets, they're often much easier to drive since your margins of error on either side of you are so much larger.
It's just a matter of what you're used to. Now when I hop into the driver's seat of a car I'm amazed at the extra cognitive load of having to pilot a vehicle ten times wider than myself where I can't see the sides or edges, where my vision is obstructed by the A-frame, and where I can't use aural cues to know what's happening around me. It's just different, not harder.
> 2. They're more dangerous for the driver.
Fair, but IMO this is a tragedy of the commons. For every car on the road that's replaced by a motorcycle, the road becomes net safer. This is the same situation with SUVs just in reverse: SUVs are often safer for the driver than a passenger car, but they make the road more dangerous for everyone else.
We should find way to disincentivize driving over other forms of transit like motorcycling, public transit, and cycling to help combat this.
> 3. They're uncomfortable in rainy weather. (And even more dangerous during icy weather.)
Honestly, they really aren't even slightly uncomfortable in rainy weather. Most motorcycle jackets will have a waterproof liner in them, helmets are intrinsically waterproof, many armored gloves are waterproof, you can buy a pair of overpants for like $20 that slip over whatever you're wearing in ten seconds and are totally waterproof.
The only thing that won't necessarily be waterproof are your shoes (unless you're ATGATT). But you can choose to wear boots on rainy days, or even if not, most shoes will hold up long enough to get to your destination (for common weather and distances in San Francisco, which GP was discussing).
FWIW I'm not arguing with your thesis that these things are often why people don't ride. It's true! I just think that these concerns are actually more overblown than people realize.