Easy accessibility and convenience plays a huge role on how huge online casino/ gambling websites nowadays.
I can say, online casinos are generating huge revenue in this current timeline by just looking at almost all of the vloggers and YouTubers are advertising these online casinos in almost all of their contents. This has even caused some issues due to it's exposure to the minors. Some were a bit of concerned so they stopped promoting these online casinos, but for many of them, they can't just turn down the huge offer so they tend to ignore the issues thrown at them.
Advertising offer depends on how popular you are and how many views your videos can generate. There's a rumor that the offer was around $2k or more for a short portion of your content tackling about those online casinos. So, I see a lot these advertisement in a lot of different vloggers in the internet. That alone proves how BIG the online gambling industry today. When a company pays huge money for the advertisement, that means it's effective and they are expanding their market as well as the revenue.