There are games with good players that are cheap enough for new players and don't require a password. My two first games were, at any rate, though one did cost 75

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But one notices the tendency for players in cheap games to go into civil disorder either for no reason or when they start to lose, even if all hope isn't lost. That makes the game worse for everyone involved. So even new players tend to try to find other players with whom they have played whom they can be reasonably sure won't fail to enter turns, simply because they want to play a good game.
Your mileage may vary, but I think the primary reason is frustration. And, of course, friends playing together, league games, or other tournament games that require sign-ups.