Similar unpopular Sports Leagues can be found all around. Please come forward and share your words on any such experience.
I wouldn't say that these leagues are necessarily unpopular, but for betting sites to be able to support them they need instant and reliable on the ground coverage of these events that simply might not exist at certain levels of the game. Semi-professional and amateur leagues might be structured well enough with good organizers, but they might be without the technology to accurately feed on of the white label scoring systems that feed many different betting sites in order to formulate their odds and historical statistics. There is no suggestion any leagues you mentioned are susceptible to this, but you'll also find that betting sites may exclude certain leagues where they think there might be a chance of match rigging and it's easier to get away with it on less watched games.