The last mile problem is much much bigger for cars. Where do u park ur cars? U need large parkings then. Parking spaces need a lot of space. Space that can be used for more housing, more commercial, more parks, etc.

The best last mile solution in this case is walking and biking. Walking doesn't require parking. Bicycles do, but they require very very less parking space.

Also, due to the non motorized nature of these two modes of transport, the public stays healthier, thus drawing less resources from the public health infrastructure.

I could go on and on, but here's like 90% of ur answer for the last mile problem.