if you get pulled by the police, most will radio in and check you have tax anyway in case the disk in your window is fake.

or if they are following a car and dont like the look of it, they will radio in and check.

the tax disks arent really needed now, most people wont dare drive with no tax due to all the ANPR vans (apart from a select few who are either wankers, or have had their heads buried in the sand for the last 10 years)

i reckon with the admin cost of producing and administering tax disks, if they took them out they could reduce the cost of the road tax by £20 - 30 per car.

other countries dont have them, but knowing our government they will keep them so they can make a bit more profit.