I thought the same however, now I think it is a good idea. Here is my logic;
Given that the average length of vehicle ownership is 18 months and it is only one part of a month across vehicle ownership then the actual "loss" isn't that great. The biggest winner for me is the fact that it now forces people who buy a vehicle to either go untaxed or buy tax - and you can't do that without insurance and MOT (if required). You also heed to register the sale. Yes, there are some ways of semi dodging this but if you do, some of your details will be recorded somewhere. It will reduce the number of people motoring without the correct paperwork.