It is really hard, and quite a drag, to go 10, 15 floors up (or down). Two or four flights of stairs, not so much. So if you had the power to design a business building and determine where each of the occupants will reside, Who would you place on the ground floor, first floor, second,... etc.?
Would you go with the busiest entity on the ground floor, and then first floor, and then so up?
Now, picture this for a minute, your ground floor has your highest traffic offices or stores. That's all fine. People walk in, walk out, and the only shared resource is the entrance and the hallway. Now let's go to the first floor. Still quite busy. Now you have 15, 20 people every minute coming in and going to floor 1. All these people are first, occupying the time of the elevator with a trip from floor 1 and then back, but since they are many, they are also taking up the elevator's capacity. Someone who is going to floor 6, may have to wait for a couple of cycles before making it.
Now, who says that the elevator has to come when it's called, and then go to all floors by sequence? (Don't worry, this is just an exercise of alternate thinking).
You may say, well, you want everybody to get to their floor fast, you don't want to penalize anybody, and you want everybody to get their fair share of the resource.
Let's see, first of all, when an elevator goes up, it stops at every floor selected, there is a rare occasion when someone wants to catch a ride to a higher floor, and then, when it gets to highest one, it starts its descent picking up people on the way.
But, Why can't the elevator go to the highest floor, and then stop on the way back? Isn't the same thing? Under this model, the elevator would go straight up to the highest floor, unless there is someone just wanting to hitch a ride up from another floor. And then, it will start its descent right away, dropping people at each selected floor, and picking up people who want to go down. The elevator will very rarely open with the awkward "we are going up" warning.
Also, if you have distributed your floor occupancy well, most of the time you will not have a high floor selected, because no one is going there anyway, and you will also provide yet another incentive for those going to the first floor, to use the stairs when it is particularly busy.
Honestly, I don't know which one is better, but what this rambling makes evident, is that when you have a bottleneck, any resource with finite capacity, it does matter a lot on how you design your process.