Earlier the gambling industry is fully occupied by bitcoin, further with the growth of ethereum it got its importance and more gambling websites started to accept it into gambling. Further more altcoins gained its importance into gambling. Even now majority of the users prefer bitcoin.
Exactly, not many online casinos are accepting other cryptocurrencies than bitcoin, i think because they don't trust altcoins as much. I still remember that couple years ago, finding such online casino was really dreadful, more of them were accepting fiat money. Right now the popularity of cryprocurrencies if growing and also platforms based on blockchain technology are setting their offer not only for bitcoin users, but also for altcoins fans.
For me it is really interesting. Recently I've found Futurobet where I can use some of my BTC also smaller ones crypto like FTO
And this is one of many examples, where even such small altcoin like FTO is accepted in an online casino. Just like in the case of Futurobet, i don't think that i've ever found an online casino that was operating with altcoins exclusively, without bitcoin