Whether you understand why they do or not, people do, for a huge variety of reasons. As for who goes for the food, no-one, certainly not with the current Bloomfield Road offerings.
You don't go for the food, but having a tasty palatable option at the ground is useful for a wide range of people.
-Dads taking their kids to the game as part of a day out. They'd need to eat anyway, so somewhere convenient to do it at the ground if there's a good option would reduce the logistics of the day.
-People traveling from outside Blackpool, their day isn't as simple as leaving home at 2.30, walking to the ground, and being back by 5.15pm. They may leave their home at 12 and get back at 8, specifically to go to the ground to watch the game. Giving them a convenient food option would maybe give them one less stop off in their day.
-People on shift work who finish work just before the game starts, or start just after the game ends, can head straight to the ground, get their food, and watch the game.
I',m sure there's plenty of other demographics and routines I haven't considered. And that's quite aside from just getting people to want to go there because the food and drink options are worth it.