That's the basic because it can easily be hidden. Dice are very small things, so you can even keep them in your palm.

Here in our country, it's different. Dice are old school. I've heard stories from the real prisoners who are now pardoned, and they say the real gambling there is mostly using cards. I guess it's because it's the traditional type of gambling here.
The bets, though, are different. It's not money but mostly vices. Well, it's given because they are not allowed to have money inside, and if you do have money in there, there's no value to it. It is power and resources that gain the upper hand.