The NIT, CBI and other associated tournaments in March tend to be ridiculed by college basketball fans as tournaments for those who aren't good enough to make it to the big NCAA tournament. However, the NIT is often a chance for many teams to get their players to attain more experience or to even improve the NBA draft stock of some players. The CBI and CIT are especially important for smaller programs.
The NIT tends to get the most odds out of all the tournaments. This is primarily due to the larger name recognition that comes with the tournament and its teams. Of course, many of the games have odds that vary based on particular matchups. In 2015, top-seeded Temple had a -13 line against Bucknell, for instance. In a much closer match between fourth and fifth seeds, Pittsburgh had a -3.5 line against George Washington.
The smaller tournaments can easily be placed on the sportsbooks as well. However, it is often easier for these to be placed on the later games in these tournaments. These include the championship games in the CBI and CIT. These are two events that have much smaller teams and therefore are not in the highest demand for betting purposes. For instance, the 2015 CIT had teams like Oakland, High Point, Evansville and Sacramento State competing. These are teams that are not typically accepted as being big draws for betting purposes.
The odds that are listed by sports gambling sites for all of these extra tournaments are clearly not going to be as popular as what's used in the big dance. However, considering how many of these NIT games and other associated games are played on days of the week when NCAA tournament games are not taking place, these are often popular options just to give people things to choose from when looking for things to place bets on.