Yes, the one thing missing that would be being able to start from a normal road, and land on something similar, which could allow pretty much door-to-door is too hard to make work for how many could afford it.
In Alaska, Montana, Idaho, North Dakota, and South Dakota, it's legal to land on rural roads.
Even in places where you can't land on roads, there are WAY more airports than you probably think in the US. It's about 19K, with a little over 5K of those being public use. (Even the private ones are often accessible with just a coordinating phone call.)
Of those, fewer than 400 are "Primary" airports (defined as having scheduled commercial service and more than 10K enplanements [commercial passengers outbound] per year).
Yes, I know there are many airports. This is about starting from "The next road with sufficiently little traffic that has suitable clearance and curvature to start from", and maybe something like folding wings inwards or so to get it small enough for maneuvering it as a large car.
