LeGeNd status regarding to Toribash is a very subjective thing since there are no specific criteria for getting it and as I know there is a group of staff who votes/decide if a clan or a person deserve it or not so talk is cheap. For me when I was a kid who played this game there were only 5 legendary clans Mad, bncy, rawr, hack and no. I don't know, maybe I don't feel that legendary status thing because I used to play since then but I believe if somebody of the elder ones would like to make their clan legendary they can force it through the moderation, sending pms to administators proving their legendarity but the thing is that they are probably too old to care about something like this.
I think the reason why they give this status to old dead clans is that they want to keep them in sight and away from a dead clan board, like making them a part of a history etc, that's the idea, I guess and that's the reason, why they do not give this status to active clans because they are still there and not going anywhere.