Many but not all gamblers are claiming they gamble for fun and pass time. I was just thinking. If it is the reason why people gamble then why not play online games?
I guess it is a matter of taste, some people prefer card games, dice, slots and other 100% luck based game than something where skill is needed.
To win CS:GO match you need to know your stuff, however, you don't need any kind of skill to roll the dice and win if you are lucky.
There is a lot of good and challenging online games wherein you can interact with other people online?
Some people don't like socializing with other people and won't prioritize multiplayer aspect of the game.
For some, the best way is to play against the odds of probability. Once again - it's a matter of taste and preference.