Interesting topic. Cities, such as they are, were primarily built around the movement of cars. This resulted in a bunch of noisy, ugly, polution-creating highways running directly through cities where parks, rivers, and other quality of life areas could be.
Freeway removal is really about shifting priorities from moving cars to moving people. This can result in people being more physically active and healthier. Studies have begun to show that those who travel by mass transport, walking and biking as their main ways of getting around are more physically active than those who primarily use cars. Freeway tear downs not only encourage more active forms of travel, but can create signature recreational amenities for cities, as most of the documented examples have.
It is obviously still vitally important to allow for cars, trucks, trains to get in and out of a city - but surely we can begin to think of better ways to do it that results in far less people with highways as their front yard.