Are you suggesting that the SPFL loan (potentially) all 42 Clubs money? Under normal circumstances, yes, they could loan a couple of Clubs money to tide them over in an emergency but not the entire league! How much money do you think the SPFL has?!
In order to advance the Club's money due to them based on their current league position they need to call the league. It's really that simple.
As for Celtic benefiting from this, I fail to see how they have. If anything, it's probably cost them another treble!