It's true that there is no fun in using bots to gamble but in some cases they can be very useful.
Other members have enumerated some of those cases and I want to add another one: participating in wagering competitions.
In those competitions, competitors tend to do what they call wager farming. They play a game like dice for example and place as many bets as possible with the lowest bet amount and lowest multiplier. This is a tedious and long process where bots can really come in handy.