betting and sportsbook site for subscription

im new here and also im learning the ins and outs of being a bookie. I have questions though if you wont mind guys me asking, is there still market for a sportbetting app (e.g.: all sports like football, esports and horse/dog racing bet app)? Are there still bookies that prefer betting on betting sites or owning their own betting app? What would be the advantage of owning one?

Cheers!