In addition to utility, road, and taxiway access, there are also often plans for hangar "lots" that require some uniformity. Our airport has space planned for a couple different sizes of new hangars. If we allowed a wrong-size hangar as the first in a new row, then we would have to require the rest of the hangars in that row to match it in order to avoid an ugly hodgepodge of random hangars. The airport also has to plan for storm water retention/detention/runoff. It may have wetlands mitigation issues that restrict building. Etc. ad nauseam.
But the airport should have some kind of a record of what the hangar space plans are. It might be a napkin drawing or it might be a professionally surveyed long-term plan, but whatever they have is what they should be showing you to explain why they claim not to have space for new hangars.
