We won’t really consider the cash out as a bonus. Rather, it is a feature that they included in the platform to help players manage their risk. In a nutshell, the cashout feature allows a player to pull out his money even before the event has finished. This is very useful for players who feel like their bet won’t go so well later in the game. It’s handy for reducing risk and guaranteeing profits.
In fact, a lot of bookies offer the cashout option, especially the newer and more modern ones.