Why can't Gil fountains be new players buying gear from crafters. Leveling 1-50 seems to give you about 100K, even if you don't try to accumulate money.
A Ponzi scheme if you will?
Because the amount of new player now is temporary. There will be a consistent amount of new player once the initial release hype wears off. Those people bring X amount of gil into the economy from their quests. That amount isn't enough to offset the amount being drained.
Eventually everybody runs out of quests unless they make a second character. They need daily quests, or do drastically increase gill payout of Leves, Hests, monster gill drops, and/or dungeon allagan pieces to equal the sink. It's possible they can also just lower the gil sinks so drastically that the small fountains we have now is enough, but it would have to be an insane reduction. The other problem would be that the best way to make money then would be making new chars to run quests , which would just be bizarre.