You’re eating at a restaurant alone. The server checks on every adjacent table, refilled their waters more than once, asks if they need anything else, asks how their food is. For your table: they take your order, deliver your food, and bring the check. You walk to the bar to get more water. It’s not busy. They have 3 other tables. They check on all of them, a lot. Just mot yours. Do you still tip 20 percent?