Monkey Mischief
The reason is simple: the customer left food under the seat.
We recommend using the space under the seat only for transporting food. Even if you leave for a minute, upon return you may find some primates near the bike, trying in vain to get your food.
But the problem is not that it's uncomfortable to ride on a torn seat, rather that you have to wait until the monkeys lose interest and leave the bike alone.
Do not approach them; they might bite or snatch something else from you, like glasses.
Less frequently, but also possible, a pack of dogs might try to get food out of the bike in a similar manner.