Betting company owners run the betting, as they are in charge of management so they may not have much time for betting. Suppose you are the managing director of a company, then do you work alone or do you manage the work of the employees working in your company? Our thinking is to make profit by betting and their thinking is to make profit by managing bets. A gambling based organization or casino based organization runs this type of activity by earning a lot of money so they don't need to play extra gambling to earn extra money. My personal opinion is like this but sometimes many jackpot offers are offered there maybe some person in the gambling establishment is betting.
There must be some rule or regulation about people from the management gambling in the casino they are managing, I'm not sure if they are allowed to do that or not because I've never read or heard about any such rule and even if they do gamble, it's not like they will or can manipulate the results and make them in their favor, especially if it's the owner itself because it doesn't make a lot of sense winning money from your owned casino because the revenue is already yours to have after all the expenditures, salaries, and stuff.
However, if a person likes gambling, even if the own a casino, they can gamble somewhere else, not to earn money because they don't need that, but just to have some fun and pass their time if they have free time and they need to do something in that free time, they can use any reputable platform for that.