Two issues with running the blower all the time. One, wear and tear on the blower over time. More importantly though, the coils in the unit need occasional downtime to let moisture drain for best efficiency. Your points on moving air while not cooling are valid though, and newer thermostats do have a circulation mode that will cut on the blower for a percentage of the time the AC itself isn't on to do move air around. Good for second story homes with one AC, as the thermostat is usually on the first floor while the heat rises to the top floor.