Good research. I'm not surprised at the conclusion: gold daily is there to be a sta sink when a "x1.5 gold found on missions" campaign week is on. Their main draw is the little playtime investment required and their low EXP reward is useful to dump sta before a level up. Not a factor when you level up so often.

The thing about gold is: when you're well leveled and stable, the natural income will be enough to cover expenses for new event girls. But in the earlygame, we want to level far more units than usual. The level up sta/gather recharge balances that out somewhat.