In multiple European cities now I see taxis being allowed to use the bus lane (while of course regular cars are not).

What's the policy justification for this?

By prioritizing Taxi on bus lane, I may rethink twice if I take my car into the city or I switch to public transportation to arrive faster to my destination. Over time this may push me from not even having a (secondary) car.

Since public taxi are at a much higher utilization than cars - 1 taxi may replace 30 cars and thus reducing congestion over time.