Gambling in any form is consider to be illegal. But since cryptos are not regulated by any government agency it is free from any accusations with regards to legality issues. Bitcoin has been use to a lot of gambling site here but none of them were restricted by the government and as long as bitcoin is decentralized no reason for it to consider illegal.
I believe gambling in some countries are legal, so your statement about gambling in anyform is illegal is moot. Though we both agree that cryptos are not regulated but still if it is used in gambling following your statment will be illegal (your statement contradict each other. @OP i think you should learn the diferent country's stance about gambling and gambling with cryptocurrency because every country have different legalities towards cryptocurrency gambling.