People with more serious disabilities can use "Dial-a-Ride", since Transport for London recognize that road transport is more suited to the final 0.0001% of the public.
If anything, it's even more convenient than going in person. I'm not spending ages having to drive to the supermarket, trudge round picking up everything, going through the checkout, loading up the car, driving back etc. I can place the order any time, from anywhere and it arrives when I want it to.