It's hard to pick just one reason, but off the top of my head:
* Any failure tends to turn flying things into unguided missiles
* Noise is extremely hard to control -- I did an FAA helicopter discovery lesson, and oof
* Cities tend to have difficult to manage wind currents and hit-or-miss visibility. I was in a skyscraper across from one hit by a helicopter trying and failing to land in 2019 -- there's reasons for city no-fly zones
* Limited landing sites makes them highly situational in the first place, unless you want your streets to be helipads, which you don't
These are all fairly intrinsic and not mitigable. I can think of more issues more in the sticks, but you get the idea.
The wind in NYC is no joke. In brooklyn yesterday there were gusts so strong that car alarms were going off. In some apartment buildings, the handicap-accessible automatic doors simply cannot open into the wind.
Imagine being in a flying car. Nope nope nope!
One more reason is that it cannot actually solve the traffic problem that it claims to solve. It might be able to solve it for rich people when they are the only ones that can afford to travel by air, but if the cost ever comes down low enough for the masses to afford it, I don’t see any reason that congestion wouldn’t be as bad or worse than it is now. And to me it’s not a good investment to improve things just for rich people.
I am (usually) not willing to assume that the founders of highly technical startups would not consider something that I as an outsider would in the first 5 minutes of engaging with the topic.
That makes me skeptical of all of these (minus the wind currents in cities, that might have taken a little longer).
There are about 80,000 non-essential helicopter flights in Manhattan annually -[0]. That means a) there is a lot of demand, and b) it’s been pretty safe, with accidents being very rare.
Many people are against helicopters on the grounds of noise, safety and pollution. Electric taxis will be welcomed once they are certified and economical. They only need to do better than helicopters.
[0] - https://stopthechopnynj.org/frequently-asked-questions/