Extra Credits - Free to Play Is Currently Broken - How High Costs Drive Players Away

I think that the thing people miss is that the income generally comes from the game itself, not whatever cash system they've constructed. The risk involved with using a free to play system is virtually the same as anything else. "Will people enjoy my game and spend money on it." Even with Maple's brokenness, people still spend money because they enjoy the game. Any system can theoretically work as long as the game remains appealing enough. It's not a matter of "can this system work," it's a matter of "is this system healthy, can it thrive."
That's why people buy cosmetics. They enjoy the game, so they spend money on it.
Any game is a risk, any game is an investment. Sure, free to play games may be marginally riskier (as far as I can assume), but it's not enough to justify foregoing game quality to rake in cash cows.

And since Maple started dying and people stopped enjoying the game, they've had to push the less practical methods just to stay afloat.