Tickets, unlike cosmetics, their quality are depends on the tournament organizers.

So by having a review system, you can protect the players from purchasing low quality services and motivate the organizers to work harder for their fans' money.

Only the people who could write/rate reviews would be ticket holders and since its not free, you somewhat prevent fake reviewers.

Its also very useful to have a sum up of stats of each games played in that tournament, how many like/dislike over the amount of viewer etc..