The knockout tournaments are a different ball game, because it is not easy for a uninformed site owner to guess who will be in the finals.
How do you suggest that they predetermine the top players, before the tournament proceeds?
matchups aren't hard to do , so at least they can offer betting for every single game at the start
outrights should be easy to add as well , I remember for WTA and ATP outrights they used to offer betting on all the players and users can keep betting till the day of the final where they locked betting right before the final game and same thing can happen here as well