Well said Pilot DAR.
The same applies to village shops and pubs in the UK. Very low support for what is an expensive business to run. Nice for a few drinks at weekends but unsupported most of the time because supermarkets sell at a much lower price.
However when the facility closes down everyone complains.
GA is not a charity and if you own land the size of an airfield in the UK it is worth several millions as a housing site.
The other problem is circuit bashing annoys the neighbours.
In the case of Biggin I am sure corporate aviation income far exceeds that of flying training.