What's the purpose of route setting? The purpose of route setting depends on the context. In a gym, the purpose is dictated by whoever is paying your wage. It's really that simple. Like in any other job, you're being paid to perform a service, or create a product, based on the mandate of your employer. It's an obvious point, but it's a true mark of professionalism that is sometimes lacking among setters. Ego's run riot, personal attachment to the creative process, and selfish setting can run rampant. Louis CK (not a route setter, but a badass comedian) breaks it down very simply:
It's totally obvious, isn't it? And yet it clarifies things perfectly. You're providing a service, and desiging a product - duh. So, who are you working for? What do they want to achieve? Trying to design routes without knowing this information is really groping in the dark. It might work out, it might not, but it's certainly not best practice. Let's go through a couple of examples to attach some real world scenarios to this abstract idea.
Let's imagine your a gym that's located in an internationally renowned outdoor climbing destination. The gym owners opened the gym to cater for the needs of the local strongman. The majority of your customers climb hard, and think of the gym as primarily a place to train. So, the purpose of your routes (or problems) is likely to be a training tool for these climbers. You're probably going to avoid making your routes difficult through setting complex sequences. Difficulty through intensity and dynamic movement is probably ok. It will be very important to dial on the grade spread in your gym, and ensure there's climbs that are at the upper end of your clientèle's limits (people who are training will quickly go elsewhere if there's nothing to challenge them).
Another example: A small top-roping gym, with no bouldering. The climbers at the gym are all inner city living folks, the vast majority of whom are new to climbing (0-2 years), and almost never climb outside. Even fewer lead climb, or boulder at a high level (V5+). The gym is a social hub with a small member base. In this situation, the purpose of your routes is likely to contribute to the fun atmosphere of the gym, and facilitate the climbers development in an easy-going way. If all the members know is indoor climbing, it's perfectly acceptable, even sensible, to have a higher proportion of gimmicky/sequency fun routes. They're here for a good time - not to get super strong for an outdoor project. Straightforward, uncomplicated, but unrelenting training style routes are probably required less often. Tweaky, uncomfortable or painful moves should probably be kept to a real minimum - who wants to knock off work for a social climb and plough through a series of cobble crimp ladders and shouldery corner climbs?
Finally, you're route setting at a formal competition. What's the purpose of the routes you set? It's multi-faceted, as ever, but primarily: to find the best climber and to create a spectacle. In splitting the field, you will need to pay special attention to ensuring that climbers are not unfairly advantaged by body type - if the routes are disproportionally harder for shorter climbers, you're not finding the best climber. You're finding the best tall climber. Similarly, having problems all of one style isn't going to work - the best climber is the most well-rounded. And the spectacle - you could probably find the best climber but having incredibly straightforward, bland looking routes, but the crowd would surely become de-motivated. This is bad. You're route setting for whoever's running the comp. If the crowd don't enjoy watching the climbers, then the interest in the competition wanes, the sponsors go away, and you aren't giving the organisers what they asked you to provide.
And so on. As you can see, the purpose of route setting can vary enormously, but the important point remains: understanding what you are trying to achieve in designing your routes is key to creating an effective product. Start here, and then go and get the holds out.