Pricing would be the thing that stands out most to me. There is really no reason that the same pasta dish on room service should cost double what it does in the restaurant.
I like dining out, I normally do so. However if I am feeling under the weather, why on earth would I go and sit sneezing over everyone in the reastaurant? Or if I am working, it makes more sense to order food in, than to go out for an hour or more. People with young children find it useful, as do those who travel with pets (even service animals).
I'd like to see price points closer to delivery food prices - after all, it is pretty much the same thing, with an elevator replacing the car for delivery purposes. I don't mind a delivery charge, but doing things like delivery charge + 22% gratuity + convenience charge on top of already inflated prices, annoys me.
The one that REALLY bugs me tho, is hotels who have taken coffee / tea making facilities out of the room, and have you 'call down' for it.