To be honest i can make few wild guesses why it is like that:
1.Now days only handful of people play games like JKIIJO or JKIIIJA. I mean, yea comunities holds themselves in good condition and are still active but ask some of today's gamers if they still play Jedi knight series. From those i meet, who play JA or JO noone knews about MBII. Most star wars gamers either play battlefront(old and new)or the the old republic mmo, only few like i said play older titles.
2.As much i love this mod, there is statement i must make: "Toxic community". Since i started playeing MBII this wonderfull but troll'ish community is one of few noticable MBII marks. New players are (if they are unlucky) decimaited by "death squadrons" of trolls and "LoL, YOLO, SWAG, noobz, iamprogamer etc." people(Luckly people like this are rare).
3.Difficult to get game system. I myself dont have anything to system and changes you did in mod guys, they're good making you require skill rater than luck most of the time but for most of jka players who entered the game its complex and hard to get, also have on mind most of new players DOSENT read and guide so they storm in as a jedis thinking they are invicible. Giving saber system in mod and few blade masters who on enemy team...well you know what will happen.
4.And last guess i can think of is, like Master LoU suggested is low or rather lack of advertising. I've never heard about mod until i seeked through moddb.com deeps for good Knight of the force mod replacement.
Well those are my statments about are dear Coke-kun's question. These are just my wild guesses, so you dont have to take them serious.
P.S I'm too lazy to correct myself, so you have to survive torture my post made to your's eyes