Using bitcoin to gamble makes it very convenient. It's easy to transfer money and you can get around the legalities easily. In fact, gambling could be a niche for bitcoin's longer term success.
I agree with you, with bitcoin most of the gamblers doesn't need to go to physical casinos just to play and gamble their. But with bitcoin they can easily gamble even to their houses through online and using bitcoin as their currency.
That's the beauty of bitcoins, it gives us the opportunity to gamble at our own home and at our desired time. With the presence of the online casinos now, we can bet of different gambling types, like poker, blackjack and my favorite sports betting.