Hangar owners got privateers for their hangars which were given by mindark as compensation opening up the possibilty of performing flights to other planets which was not possible with the old hangars which only were hosting shuttles to reach calypso space.
The 'new' hangars were an optional building given out by the planet partner FPC who was in charge for planet calypso at that time. Planet partners to this day still have the possibilty to sell hangars according to their population limits but these are just buildings without space functionality and at this point in time more like special warehouses which are valued by some as speculative estates in hope of future space functionality.
The reason there hasnt been any new hangar buildings sold by other planet partners is most likely to not give participants a false impression and/or to wait with such a possible sale and only perform it when these buildings actually get a space related purpose restored to them.