Several reasons:
1) To install it and make it look somewhat not fubared took me two to three weeks. Mind you, I am not an idiot when it comes to modding in PHP.
2) The guy who did the one that was mostly compatible with our site stopped support and adding games. They can't be any flash games, they have to be changed to work in the PHP world. Some people got real shitty with him for using their flash, but they were idiots (it is called promotion, dumbass, crybabies). He may have started it up again, but I wouldn't use it again.
3) After an extremely high score was attained, everyone stopped playing the game(s). I would monitor the usage and probably for the last year or so, there was seldom a game played. Granted, games should have been added, see #2 for this.
If I come across one that fancies me, I may give it a go, but as I have stated in the past, I am not in too much of a rush to mod, this being our fourth or fifth board.
i know 2 good sites for them. 
