And where would these Motability branches be located?
At least using the current main dealer network keeps Motability’s overhead costs down. Imagine how much it would cost Motability to create from scratch a branch in every major town and city in the UK? Costs such as land, rates, staff (both sales and vehicle technicians etc), to say nothing of the individual manufacturer training each would need (from every manufacturer on the scheme).
It would simply be unworkable and financially bonkers.