They have a terrible reputation, primarily because they get used a lot by people who can’t afford a car.
I wish it were different, but driving a moped/Vespa on American roads is a pretty big risk.
Why do you think that is? (genuinely curious)
Of course, I don't see things this way anymore but I'm fairly confident that this is a common mindset.
Anything that is “surprising” while driving cause stress and anger reactions.
Conversely being on a bike there is a real sense that people in cars are out to do you harm. Theres the people who try to rattle you - honk their horn at you to vent their outrage, completely unaware of how fucking loud those things are, or run you off the road, that sort of thing. The real unnerving stuff is the people who come close to murdering you by accident, just not paying attention as they maneuver their vehicles. One time I made eye contact with a woman while I pulled my bike out from under her SUV (just a foot or two under, right between the wheels on the passenger side, real lucky break for me) as she sped away - people do hit and run but I never experienced it as a driver and don't think a car ever stopped to see if I was alright let alone exchange details when I was on a bike.
I never got the impression it was a class thing. I think part of it is that a bicyclist is not at all threatening and rather vulnerable in fact. The other part I suspect is just regular old 'not one of us' shit - if you listen to people they'll basically tell you how they think they should be allowed to wantonly mistreat bicyclists because they felt mildly inconvenienced at one point.
If a driver runs a stop sign, it reflects badly on that driver. If a cyclist runs a stop sign, it reflects badly on ALL cyclists, etc. It works the other way around too.
The same people think Bicyclists aren't trying to get from A to B but are just out for a ride and happily breaking the unwritten rule. That is where the outrage comes from, they think the cyclist doesn't care about the irritation they're causing the drivers so the drivers decide to take it out on the cyclists.
Apparently this is not uncommon, almost routine. The driver ran off, and the next day another person - not the real driver - turned himself in to the police. Apparently the Mafia has sone exchange program with the garbage companies, they do each other favors. Somebody will now sit in prison for decades, for a murder the detective knows he did not commit, apparently to repay some debt. And my brother-in-law's murderer is still driving garbage trucks on roads with cyclists.
The biggest difference is there are more protective laws / dedicated bike lanes and the critical mass of cyclists means you might be swatting at a bee swarm.
Plus, there just aren’t very many on the road so they stick out as unusual.
And there is a cultural obsession with big vehicles being tied to masculinity.
Which means that many (15%?) drivers would feel happy or even a little justified to blow past a moped on the road.
This is definitely regional. In California, social status (/"masculinity") is tied to luxury brands. Especially in the metros, if you were driving a giant truck you're going to be laughed at (more often than not) as parking is going to be impossible for you and you're going to be spending 150usd/5days to fill up.
In Cascadia/Northern California, eco-drivers (Prius, Tesla, etc) are seen as the self/entitled assholes.
And in Colorado, it's people with AWD/4WD cars (especially, Subarus and Jeeps).
"Trucks" as a social status signifier is confined more to more rural and Southern states.
In practically every country in the world, this experiment resulted in people giving money to the poorer neighbour. Only in the US did they give it to the richer neighbour.
[0]: https://www.urbandictionary.com/define.php?term=DUIcycle
Primarily because they are slow and constantly get in your way, building a train of cars and making many people late for work.
