> Because they're not paying for the cost of the road capacity they're using.
Suppose it costs $3000/month for an apartment near where you work, because supply is constrained by bad zoning regulations etc. If it costs $1500/month + $400/month travel expenses to live an hour's drive away, lots of people will do that instead. If you add $1100/month to the cost of driving to discourage that, all that happens is that the $3000/month apartment goes up to $4000/month because you've increased demand for closer housing but not supply. If there is no housing for people to move into, there is no price that will get them to move into it.
But if you increase the supply of no-commute housing then people will immediately move into it independent of the cost of road capacity, because landlords don't want empty apartments so the price will fall to the level that causes the new units to be occupied.
If you add $1100/month to the cost of driving to discourage that, all that happens is that the $3000/month apartment goes up to $4000/month because you've increased demand for closer housing but not supply.
That's not all that happens. You also see an increase in the population living close to work (even without zoning changes, you'll have more people living in the same set of units) and employees demanding higher wages for working in inaccessible parts of town, and companies responding by moving offices to places where they can get cheaper workers (i.e., places which are more accessible).
> You also see an increase in the population living close to work (even without zoning changes, you'll have more people living in the same set of units)
Everyone gets squeezed into a tin can in probable violation of zoning and fire codes, when instead we could build nice new housing for everyone.
> employees demanding higher wages for working in inaccessible parts of town
Which some of them would get but it would only go directly to rent. Which prices the existing occupants without higher wages out of the space, and makes high housing costs even stickier because landlords never like to see rent decrease and now have more incentive and resources to fight against it.
> companies responding by moving offices to places where they can get cheaper workers (i.e., places which are more accessible).
Another way of saying less density and more sprawl.
Suppose it costs $3000/month for an apartment near where you work, because supply is constrained by bad zoning regulations etc. If it costs $1500/month + $400/month travel expenses to live an hour's drive away, lots of people will do that instead. If you add $1100/month to the cost of driving to discourage that, all that happens is that the $3000/month apartment goes up to $4000/month because you've increased demand for closer housing but not supply. If there is no housing for people to move into, there is no price that will get them to move into it.
But if you increase the supply of no-commute housing then people will immediately move into it independent of the cost of road capacity, because landlords don't want empty apartments so the price will fall to the level that causes the new units to be occupied.