Most cooking tools are about producing a great dish. And certainly the most important things are taste and appearance: The food we most want to eat both looks and tastes appetizing. Unfortunately, achieving those qualities doesn't end when the food is cooked. It ends when it makes it to the table and into people's mouths.
That's where a warmer comes in. A warming drawer, typically positioned below the oven in a range unit, although it can also be a totally separate device, can get plates and bowls warm so they help the food stay hot once you plate it, and it can keep plates of food warm until you're ready to bring them to the table.
It's a luxury, no doubt, but one that could be worth the investment if you're into a professional-grade meal. Even the best-cooked hot food starts to go downhill as it cools. There's not much point in cooking your Alfredo sauce in a nonreactive pan over a gas flame if it's just going to congeal by the time you sit down to eat it.