Revolvers have lots of tiny, little internal parts. They are delicate, and get out of time easily.
Revolvers are thicker, and therefore harder to conceal.
Further, it is very difficult to reload a revolver quickly.
The advantage of a revolver is more emotional and ephemeral than it is real.
Revolvers have just as many drawbacks as do semi-autos. It's just that they have different drawbacks.