Polluting - I don’t think so, except they’re 2 stroke engines, which are rare, nowadays. These days you see even more and more electric bikes.
Inefficient - People often go 2, 3, 4 people on a bike that uses maybe 3 l/100km (78 MPG) or pull trailers wich stuff loaded, while using less space than a car.
Unsafe - totally less safe for the people on the vehicle. I don’t know about pedestrians. However, a lot of the accidents happen, because poor education to get the license, if any; hardly any law enforcement and poor vehicle maintenance.
Noisy - not more than a ICE car. Some motorbikes here have broken exhausts, which make them noisy, but that again is a lacking law enforcement and maintenance issue.
I am aware, however, that driving 2 wheel vehicles in ice and snow is not a wise idea, so while it works in SEA, it would be different in colder climates.
Gasp! Oh no! Scientists are STUNNED IN DISBELIEVE! You won’t believe what they ALARMINGLY discovered! /s