Projects often need money immediately, in order to START producing towards their goals. These funds are non-refundable to ALL contributors/investors.
Personally, I'm a big proponent of having "traction" BEFORE receiving funding, but that is NOT always feasible. In this case, I believe 10% is NOT too much, but should be enough to get things moving.
Projects are FREE to treat this "petty cash" as disposable income for whatever purposes they see fit. It would be advisable to them to make good use of it, or face tightening of the distribution of their DRIPP, or the possible exit of all contributors all together.