It's definitely becoming more and more prevalent as time goes on, due to more and more methods available online to gamble with and more sites with little or no verification required to deposit and withdraw. There's two sides to crypto-based gambling, and this is the darker side.
As for CS:GO Skins and items associated with gambling there, I believe everything really started with the concept of cases to unlock skins, starting sometime in 2013, and gambling with virtual skins really began to grow around that. There's definitely some actions being taken by Valve to stop this, including cases being locked with no option to unlock in Belgium and the Netherlands, as well as the regular banning of gambling site bots to stop sites from operating, though.
It's not the darker side of crypto-based gambling, it's the only side of it. It just doesn't make sense for a gambling casino to require your identity and they sure are going to lose players when they do that or they might not even get players at all. Even if gambling is legal in your country and you're at a legal age, why bother registering in a gambling site that requires identification when you can simply register to one that doesn't?
The betting system in most games doesn't really feel like you're gambling since for one, you're not really betting real money. And I think this is where gambling habits start as a kid. Although we really can't put the blame on online games that have a betting system because ever since, gambling has been a common thing in our society. Even when it's frowned upon, everyone's either doing it or has done it.