In Chinese, 八, meaning "eight," is pronounced "bā," which rhymes with the word 发, "fā," meaning "to make a bundle of money."
8 in multiples, such as 888, is especially lucky. In gambling most Chinese people are extremely superstitious when it comes to numerology.In everyday life, Some will pay up for lucky number 8 in everything things, such as custom phone numbers, license plates, etc.
So casinos having $8 chips is mostly pandering to the rising wealth of the Chinese. It is usually combined with the Chinese zodiac cycle for Chinese New Year. This practice, at least in Nevada, appears to be ending. The commission frowns upon commemorative-only chips that do not have practical table game usage. 8 does not serve practical purpose. So they are reverting back to $1s now.
Along those lines, the number 4 is the opposite. It is extremely unlucky. 4, pronounced "sì," sounds like 死 "sǐ," meaning death. Some buildings in China (though mostly in rural areas) will not have a 4th floor, just as some buildings in the US will not have a 13th floor.