Food carts on low-cost airlines. Not everyone is going to have a meal but the crew must take it around. This creates a great inconvenience for passengers who might want to sleep (in early morning flights) and for those who want to hit the rest rooms. Especially for those stuck between two of these carts.
Most airlines today allow booking a meal while making the reservation (albeit only if you are going through their own reservation system). It is convenient for meal time flights (early morning, afternoon and late night. They should extend this to the check-in counter. Order a meal during check in. Or even have that option in the kiosks for check-in. Then the airlines deliver the food directly to those who have already placed an order. No carts involved. For the rest of the passengers make it on demand.
The downside for the airlines is they lose impulsive purchases. But I feel making the decision at the check-in counter may prove to be more impulsive. You have less time there and queue waiting behind. Ultimately it will be more convenient for the customers.