Every year, billions of vehicles worldwide shed an estimated 6 million tons of tire fragments. These tiny flakes of plastic, generated by the wear and tear of normal driving, eventually accumulate in the soil, in rivers and lakes, and even in our food. Researchers in South China recently found tire-derived chemicals in most human urine samples.
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.