Taxis but not cars

Driving around the center of Dundee earlier this week I was again annoyed to see a road marked such that taxis may turn there but other cars may not. Some places have roads that only taxis may enter, never other cars. I remain puzzled: why make me take the long way around in my car or maybe not get there easily at all? My car is smaller than a typical taxi, I am less likely to stop for long at an inconvenient place waiting for some customer, I am sometimes ferrying disabled badge holders about, etc. I really do not see why taxis — well, those who can afford to pay their fares — should get special privilege in this regard. If the problem is one of people actually parking instead of just waiting then some actual enforcement would not go amiss. I often find that irritating policy is well-intended but poorly aimed.