I agree that this is a simple and clean solution. But for large app or games it's not efficient. Suppose @peakd want to delegate a small amount to each new user (and hopefully the number will go way up in the future). We'll have to micro-manage thousands of small delegations and keep doing minor adjustment to the delegate amount according to how much each user is using.
Having a pool that is shared and only 'consumed' as needed is much easier and more efficient for this scenario.