I suppose if I had to consider a specific market as you mentioned I would target the "masses" and use the "easy to learn, difficult to master" style of gameplay in order to possibly draw in the "hardcore" gamers as well. I don't understand why a game can only target one crowd.
I'm guessing you would probably attempt to target a game in production towards a market for a few reasons (someone actually in the industry will have to back me up or shoot me down):
1. Makes it easier to focus game design to certain aspect. For example, if you're designing some sort of traditional role playing game, you traditionally don't include straight first person type combat (I'm not saying that it doesn't work - see Mass Effect and Oblivion - its just not traditional). If you're trying to reach "everyone", you stand the chance of watering down the game's various parts.
2. Makes advertising and marketing easier. For example, role-playing games can be advertised in Fantasy magazines, Roleplaying magazines, on those websites, etc. Again, trying to reach everyone is expensive.
3. From a business standpoint, a target market can also be used to estimate a profit for the project. If a company is to survive, it has to make some money somewhere. So, companies need a method to determine if a project should be done or "passed over". Based on the same concept of a large industrial purchase, corporate-types probably analyze a game based on production costs versus expected profit based on target markets (which carry some type of known, expected average profit margin) - if its positive profit, they'll take on the project - this is possibly a reason that crappy, crappy games associated with movies come out. (On a side note, this allows companies who have already released enough profitable projects to release a concept project or fun project.)
Besides, making a game "easy to learn, difficult to master" is probably one of the hardest things that a game designer can take on. That's just from a balance standpoint. Add this to it: how do you define "easy to learn"? Do you mean easy for your grandmother, or easy for your fifteen year old, or easy for the average gamer?
So, targeting a game for a particular market is helpful on several levels. I can see why it happens. The real difficulty is what yaustar brought up: why is it that brilliant games that "should" transcend markets fail? Why do games that don't even seem like games succeed? How can you determine when a game will make that leap?