Why do we play Maplestory?

I suppose that would be one way of looking at it.
It's just when you stop at a fairly short level range and refrain from progressing, you can still technically have fun screwing around, but you're not really playing *the* game, but using it as a platform to make your own games.
If you choose to actually progress further you eventually find that doing so becomes increasingly impossible without NX.

While I agree in part with your statement I want to just play devil's advocate and say that on the other side of things there could be those people who just don't enjoy leveling after a certain point and would just rather PQ with others for fun, or level up their trait skills/make items to sell, or just be a mercher. My point being is that yeah the main idea of the game is that you level up and increase your skills but again that's only 1 aspect to the game.

Though I have to say I am one of those people who doesn't see the point if you aren't going to aim for a high level and good gear...but again, just my mindset and I respect other peoples' choices in how they play the game.