If there is one thing that computer game designers and sports coaches, have in common, is that they realize the importance of practice.
When one first looks at any good game/sim, one first looks at the flavor, the theme. One might look at what the levels are, or what the tasks/quests are that challenge people to accomplish something.
But what is really being developed are underlying skills.
The skills should be developed carefully, one or a few at a time. Then increasingly mixed and matched, allowing effortless use and improvisation.
Sims, unlike their cousins role-plays for example, are interesting because they can uniquely fill this need to allow for systematic skill building through repeated practice in a controlled environment. This subliminity of practice is a sine que non of developing skills, both big and small.
You don't have to use simulations, of course. But if you don't have practice built in, nine times out of ten, your program will be wasting everyone's time.