The number of places in the US where the situation you mentioned is reasonable and public transit is not also good enough to go car-less is very small. Carrying groceries on a moped is doable but a pain. Commuting on one in the winter isn't exactly fun either. Carrying kids on a scooter is a great way to meet every cop in every place you drive through. I wish mopeds were more practical but there's a bunch of little reasons that add up to them not working as well as a cheap car.... which is why pretty much nobody around me except a bunch of single people under the age of about 25 rides them.