Because that's what those games invariably degenerate into, if they didn't outright start that way. When your main income source are the idiots willing to pay real cash for a +20 Sword Of Ganking or for a Level 3 Mech in a Level 1 Battletech-like game, guess which group does the game catter to?

The thing that you're missing about Puzzle Pirates is that the most of the really big, expensive items don't actually give you an in-game advantage. The custom portrait of your character hanging in your fancy house or the parrot riding on your pirate's shoulder may look cool, but they don't actually affect game play.

Those items that do affect game play are priced so that it is just about as easy for a kid to obtain them by investing a few after school afternoons as it is for an adult to obtain them by investing the fruits of a small portion of their work day. And this is further balanced by the fact that most of the expensive weapons are difficult to use -- it takes a fair chunk of play time before you are going to be skilled enough to be effective with them.

The beauty of Puzzle Pirates over other MMPORGs is that in-game rankings are ultimately related to actual puzzling skill. Your level does not depend on how big your weapons are, or how much time you've invested; it depends directly on how good you are at playing the game, and that makes Puzzle Pirates, to some of us, at least, much more satisfying to play.