They dont bother retracting because the they still are running all the in-flight checks during the retract sequence. ie there would be a minute of checks before and a couple of minutes of checks afterwards.
Therefore it doesnt make sense to retract during what is a fairly short display.
As for ballast, the first flight was not that close to MTOW, but the aircraft does carry a large number of drums of water. The water can actually be pumped around between drums (probably to explore CG variations and ranges).