Such a bonus is a casino's way of extending gratitude to players who choose them over the multitude of houses available online. It poses great benefit for the player in the form of being able to know how various games in the house operate without having to use their own money.
In the year 1872, Jamaica imported the mongoose to get rid of the rats in cane fields. As one of the added benefits, the mongoose killed almost all snakes and finding a snake today is difficult. Even though the government allows tourists to place live online gambling bets, it does not let the locals do that.