What's the point? Passenger comfort! Make the ride nice for the people that are paying the company it's revenue. Give htem a nice, cool, no-ear-bump ride and they might come back.
In the little Boeing Mad Dog, there is only an advantage going packs off on short runways (about 4% RTOW advantage). There is no advantage on a long runway because the packs shut down automatically if an engine fails when airborne.