Bitcoin gambling is growing due to a few factors.
Transaction time is quite fast and users do not need to vertify themselves to gamble in bitcoin unlike in fiat.
Agreed, the old days of having to find some way to get your money transferred to malta or wherever was a pain. Bitcoin makes it much easier... people still don't trust online gambling though. I think it will always be a niche and not much more than that when compared to vegas or whatever but I think it makes it more accessible.