Let's look at this from a game theory point of view. A self-imposed cap is a signal to potential contributors that you don't intend for this particular project

Let's look at this from a game theory point of view. A self-imposed cap is a signal to potential contributors that you don't intend for this particular project to exceed some specific aim. Sending this signal lets contributors differentiate between these types of kickstarters, which seems to be the problem here.