Why aren't there more passenger helicopters?
Airplanes are much more efficient, much faster and scale better.

Helicopters are limited to around 150 knots because when flying forward the tip of the advancing blade must not exceed the speed of sound while the retreating blade must still move aft fast enough to produce lift.

Helicopters are also difficult to make large, because for efficiency the rotor disk needs to be large, but the diameter is again limited by the tip speed having to remain subsonic. And the material requirements to make the blades strong enough without making them too large to keep drag low.