Mrees, you agree with the quantity > quality because as you said it's better to have 10 good set up servers rather than 100 fails. Maybe you missunderstood the meaning of the word O_o
Now as about the private servers : L2J
From Wikipedia, the free encyclopedia
L2J is an open source server emulator based on Java for the MMORPG Lineage 2, which was developed by NCsoft. The emulator was first started by L2Chef but numerous other developers have contributed to this project as well. This emulator allows anyone to run their own Lineage 2 server.
L2J servers do not require players to modify their clients in order to play. Instead, players are required to edit their hosts file found in the Windows system folder.
L2J is programmed in Java for portability, and is compatible with any platform that can run Java Environment 1.6 or greater. On a powerful machine with well customized settings, an L2J server can support more than 1000 players.
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Criticism
At the current stage, compared to retail servers marked as "official" (stolen from original developer and owner), L2J has a few game elements missing or not working correctly. This can lead to some degree of gameplay imbalance. L2J was also plagued by crashes and inefficient use of server resources in earlier versions, leading to many players avoiding private servers running L2J, opting anstead to flock to servers running official leaked, or in some cases, original software unrelated to L2J. These issues have been largely resolved now however with many L2J servers now being nearly as stable and feature complete as official rip based ones. L2J always support the newest game client, but sometimes they miss some old features from old versions.
Source : http://en.wikipedia.org/wiki/L2J
But after all that, I mean after what wikipedia mentions let's get on topic and answer to the author's question which is "WHY" they make fail servers not why there exist fail servers. At least from what I think. ;)