[Dr. Sivana]

Why do they have a hole in the middle? What value does the hole bring?

I know the answer for donuts, and it may apply to bagels, too. Without the hole, the middle of the bagel would be undercooked. Plain donuts have holes. Donuts with filling (e.g. jelly) don't need holes because the center doesn't have to be cooked.

[Freest Republican]

According to AI that is part of it and:

Bagels likely originated from 14th-century German immigrants who settled in Poland. These immigrants brought traditional pretzels with them, which eventually transformed into a more rounded roll with a hole in the center. These round breads were called “obwarzanek”.