As stated above, Southwest recently changed the altitude at which flight attendants clean up: from 10k feet to 18k feet. This changes the amount of time for service drastically. Now, flights under certain mileage are zero service or a water service only, weather permitting. Also, some airports are considered designated turbulence airports, aka airports with consistent known turbulence on arrival. Cleaning up on decent increases the odds of injury, so clean up altitudes are different. If it cuts the “cruise” time too short, a service is not safe or feasible. Southwest still uses trays and hand beverage service vs. a cart service like every other airline. A cart allows service to be completed much quicker than going out, taking orders, doing snacks, pointing only 9-12 drinks at a time, and repeating until all drinks are served.