Well, since half the households in the US earn (BEFORE TAXES) less than $45,000, a $6,000 scooter that won't carry the kids to school or groceries for four to the house, might be hard to sell. That $6,000 is 1 1/2 month's wages. Now add climate for a variety of areas of the US, and we're talking about a seasonal vehicle.
It's not even expensive to the average wage earner tbh. They just need to be shown a reason to buy.
That said, you are very correct that the "Yacht Club Crowd" wants something more laden with artificial testosterone than a scooter. I had fellow members in virtually every yacht club to which I have belonged who spent a pretty sum on boats that rarely left their moorage. But they all had a Yacht Club decal in the window of their luxury car. What was really funny was that they would ask us how we could stand to pay the cost of fuel for the months of cruising we did every year. Again, it's all about perceived needs and how we might want others to perceive us. Some of us belong to yacht clubs because that's where some real boaters hang out, and others because of the implied prestige. Kinda like vintage vs modern being two totally different tastes in scooters.
There are a lot of hurdles involved to get Americans to 1) experience the joy of riding. After all, a license is required. and 2) find utility in a scooter. What are you going to advertise? The US is a 4 wheel culture, and has been since shortly after WWII. Piaggio saw a need that cars were too expensive to fill, and continental Europe became a two wheel culture. When the need for a more highway capable vehicle arose, people were ready for a PTW to rise to the occasion.
Generalizing the motives of the US population that currently owns Vespas to be inherent in the rest of the population is just folly. Just as inaccurate as equating my 60 year old neighbor's reasons for riding her PTW to that of yourself. Her 125cc scooter is all she can afford. She's had it 10 years, and has no interest in anything other than it continuing to provide her with reliable transportation. Other than scooter ownership, you probably have very little in common with her for why you are owners.