Even if it's not grand new features it hurts innovation. If you have to sideline a product that's being worked on because sales sold a feature that doesn't exist and you have to hack together a solution quickly, by definition of it being a hack it probably isn't going to scale well to other customers. And even if it does, you are not building a cohesively product at this point, you are creating a product that caters to the wishes of a specific clientele who, by the way, probably wouldn't have a problem up and leaving your business if someone else is willing to cater a little more.