Bus lanes and taxis

(Source: Idlan)

I've always wondered, what's the point of letting taxis into bus lanes?

Sure they are public transport. But they are more like private cars, aren't they?

They require the same amount of space as cars, are only capable of moving the same amount of people as cars, but why are they given the privilege of using these lanes?

I think letting taxis into these lanes is counter-intuitive.