Because there's at least two additional parties to concession revenues beyond the venue operator: the home team, who often takes up to 50% of the revenue, and concessionaires, who employ the servers and supply the actual food.
Venue operators and sports teams don't like the liability and cost exposures of serving food, so they farm it to a third party. And rather than carve that up into multiple competing vendors, most modern large venues hand it to a single hospitality company, who uses scale to lower costs and offer a lower share of revenue in exchange for exclusivity over all venue food service. Without competition, they can jack the price up.
Worth noting two things on the "why not raise ticket prices" angle: ticketing is moving in the same outsourced direction as concessions, and ticket prices are going up anyway (up >100% since 1999[1]).
> Across pro sports, Matheson says, teams are making the determination that "they can make more money selling fewer, more expensive tickets rather than lots of cheap seats."
Most venues have given up having their own box offices and farm that out to StubHub, TicketMaster, etc. Same motivations, same result: the venue spends less by contracting out ticketing, the team gets a bigger cut of the revenue, and the ticket vendors get exclusive control not only over selling the tickets but reselling them, with dark patterns like dynamic pricing and fees piled onto the buyer at every part of every transaction.
Both wipe out all competition on both quality and price. Everyone benefits from it except the consumer, who's the only party who can't choose. Apply that pattern to existing fanbases grown over generations during eras of better prices or quality and you get a captive audience who complains constantly but never quits spending, so there's no pressure to lower prices or improve quality.
1: https://www.npr.org/2025/10/23/nx-s1-5561909/ticket-prices-s...