Not really. They do it many times a day, depending on how long the ride is. When people take busses and cabs, they aren't needing parking nor contributing to traffic. If 15 people take a cab instead of driving in a day, that is 14 less cars on the road. This is the main point in general. The traffic with cabs is a bit different - you know how many cabs work on any given day (on average).

I guess you'd be shocked to learn that here, not only can taxis use bus lanes, but so can electric vehicles to help encourage better choices.