With trial & error, the original cracker bakers learned that the cracker cooked more evenly with the extra holes as the hot air circulated better thereby more even cook time & a crispier cracker. Once corporations began to mass produce the cracker, they chose to not reinvent the wheel & stuck to the original recipe & method of cooking.
The best part of bread, bagels, pancakes, and crackers is the edges, because they are slightly burnt which produces a very light caramelization.
Holes in crackers increase this effect by adding more edges.