There are still people who do not know the use of this small hole

This prevents the padlock from rusting, prolonging its life and use.

Alternative to the Padlock Hole
While the padlock’s tiny hole feature was once revolutionary, weatherproof padlocks are also on the market. This design ensures a padlock will continuously ensure your belongings are safe all year round.
Another Reason for the Padlock Design

In addition to safety from rusting, the tiny hole on the bottom of a padlock fulfills another important role. Sometimes, the padlock may become stuck or unable to open, even with a key or correct code. As such, the hole can be lubricated synthetically to help the padlock pop open.