Assuming for a minute that a school makes $100 profit per hour of flight training, that's $4000 profit per PPL that goes through to completion.
I would be surprised if many flying schools are making profits like that, I know we certainly aren't!
Precisely the reason why I used the word revenue rather than profit.
Aware the profits are not necessarily huge, however assumedly there are still numerous fixed overheads that can only be covered by additional cash flow, and the best way to achieve that is to not turn away potential customers