We think of walking as a rather simple task that the majority of the population does everyday without thinking. In reality, its actually quite a complex process that requires numerous brain areas as well as your senses constantly providing feedback.

The main motor system consists of your motor cortex with upper motor neurons (in the brain), your spinal cord with lower motor neurons, and the muscles they innervate. All those need to be firing in a complex pattern (tense the quad of one leg and release the hamstrings while doing the opposite on the other leg for example).

We also need to maintain balance. We do that by taking in 3 sensory inputs: the feel of the ground beneath our feet, the orientation of our environment with our eyes, and the placement of the fluid within our vestibular organs in our ears. All of those systems combine within the basal ganglia (like the thalamus) and the cerebellum to drive changes in our gait that allow us to stay upright even on uneven ground.

Walking is also a rhythmic motor movement so we need to maintain an even pace for each step. You can imagine how difficult it'd be to walk if every step went a different distance or your speed constantly increased or decreased. The cerebellum also is in charge of that and modifies our gait to maintain a certain pace.

All that is required just to walk on a treadmill. If we're also in a complex environment, let's say a sidewalk, we're also going to need to use our prefrontal and premotor cortices for planning future movements. If someone is walking in front of us, we'll need to plan a route around them and maybe speed up a little to pace them. If you see someone start to cross the street and they may intersect our path, we now need to calculate how fast they're going, the most probable path they'll take, and how we can change our own gait to prevent collision. Of course nearly all of this is done unconsciously without you even realizing it but it all needs to happen to successfully navigate just a sidewalk.

All of this is to say when people can't walk, there could be a multitude of problems and all these pathways contain millions if not hundreds of millions of connections. So there isn't a simple solution of reconnecting the pathways since its incredibly complex. Spinal cord injuries, uncontrolled diabetes, strokes, Parkinson's disease, amyotrophic lateral sclerosis, cancer, vertigo, etc are all disease that make it hard to walk but they affect different pathways.

Pyramidal system (motor cortex) - https://www.ncbi.nlm.nih.gov/books/NBK540976/

Extrapyramidal (everything else) system - https://www.ncbi.nlm.nih.gov/books/NBK554542/