I don't know about the cheap cheap airlines but the major carriers include "food". Food being little snacks like pretzels and a drink since most domestic flights are typically short. You can buy a "boxed meal" if you want and if that flight has them on board. You can always buy booze, not cheap. First class, on long domestic trips, you get a meal included in the airfare and always free drinks/booze.
International flights....everything is included in the ticket price, including booze. You get meals at certain times of the flight and can ask for drinks/booze whenever, but you prob have to get up and get it yourself. First class international you get WAY nicer meal options and can eat anything they have at anytime. They took desserts away on Delta first class during covid but I believe its coming back this year, lol.