That is a very good possibility. Local shops are often busy on Fri. making pizzas for people who are attending these games. The wait time at my local shop is generally highest on a Fri. night. Also, local shops may not be able to offer a reduced price on a large order to enable the concessionaires to exceed the profit margin they can get from selling what the chains supply them.
Additionally, why do people like to eat at chains or get fast food when they're out of town? Because, even if it's probably not the best meal around, they know what they're getting.