Now that you know what betting lines are, you're probably wondering who comes up with them. Does Las Vegas just pull the numbers out of thin air and go with what sounds right? Uh, no. As we mentioned earlier, sports gambling is a billion-dollar business, so a lot of thought goes into creating betting lines. And while companies like Las Vegas Sports Consultants have helped sportsbooks create lines in the past, just about all sportsbooks have in-house oddsmakers that are in charge of creating betting lines in the weeks and days leading up to games.