The problem is the number of people on the Scheme is increasing. There are limitations but if you choose wisely (from the vehicles available) it is still a cost effective method of having a car.
The gap is closing and the limitation on how far £61.20 per week can get you in these uncertain times is starting to show. Motability are, and have always been, risk adverse and will always overcharge if there is even the slightest risk of them undercharging.