I wonder why all the casinos are stuck at this level? After all, 0.5% will give the same results, playing dice people make thousands of bets and the result will be the same.
This is probably an industry standard that most casinos stick to. Casino house edge determines how much profit the casino makes over the long run. Basically, if a casino decreases its house edge, profits will decrease as well, and that probably won't be sustainable. If they increase the house edge to make more profit, gamblers will look for a new place to gamble. It is a delicate balance.
There are some casinos with a higher house edge on the dice game, such as Freebitco.in, but they attract players with a wide range of other bonuses. On the other hand, some casinos began with a lower house edge in their early phases to promote their brand.