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Imagine no defenders at all. Two targets to choose from: One with a half dead town, and a pristine one. The easier target is the latter one, as issues with rebuilding targets are avoided.
Going back in time. Small maps, few fields, many players. Such thing as an undefended field didn't exist, except on the other side of the map. The targets nearby were often partially damaged. Fights would continue due to lack of patience, and a higher ratio of people not understanding the issue with rebuilding stuff, hitting things randomly out of sync. A well-timed attack could turn a fight into a capture. Not by contributing much to the fight, but hitting things at a time when everything was up.
Attacking fields further away was an option, and paid for with a longer trip, or possibly low-E state at the target by going NOE. Less defense was a plus, but a huge advantage was that this avoided rebuild issues.
Today, there's almost as many fields that can be reached easily as there are players (well, EU primetime, with 15-20 in-flight per side). Unharmed fields do exist in large numbers. They are also undefended. Fighting for a capture doesn't make any kind of sense.
What is the proper way to drop supplies on town? Its not to bring all buildings guns up as fast as possible. Its to get the drop distance right to rebuild only part the town, sufficient to prevent capture. By the time that resupplied part be destroyed again, the non-supplied part is closer to rebuilding on its own.
There should be an incentive for persistence. It should be easier to capture a field that's partially destroyed than one that hasn't been hit at all. A badly hurt field should need more defending players than a fresh one.
I don't think that is possible with the current way how destruction/rebuild works.
Possible solutions might be a minimum time of air/ground superiority requirement for capture, or the possibility to prevent things from rebuilding while they are down (supply trucks are one way, but their destruction cannot prevent rebuild even when the field is under continued pressure).