Multifamily housing is generally cheaper in high land cost areas. It helps solve the housing shortage.

More bikes and transit and fewer cars means cleaner air and fewer traffic deaths.

Less fossil fuel usage in general means less pollution.

Cities that use land more efficiently tend to be more walkable, pleasant, and don't gobble up things like farmland or forests outside the city.

Come to think of it, less beef is probably better for your health, too.