For me it depends on what is the most and easiest access for gamblers whether online or offline though I don't have the data for each games but I think card games will be on this list as it can be played online and offline. Here in my place and country as a whole it is the most common gambling game you will find on each towns aside from cock fighting, cara y cruz and lottery which is not as common as card games do.
There's no type of gambling that is not addictive and there's also non that has less or more of gambling addicts. As long as an individual can be addicted in gambling, they can actually be addicted in any form of gambling activities, whether online or offline. It's takes discipline and determination for a gambler not to be addicted.
Many gambler are gambling are addicted to the games that they are familiar with. A gambler who's betting on sport games and is very familiar with those games can not get addicted to crash games because he is not familiar with those crash games. Addiction is like a disease, it drains the money of a gambler, but no matter the kind of games a gambler is betting on, if he's not gambling responsibily he will still become addicted to it.
This is serious problem and it doesn't matter whether they are fans of sports betting or various existing casino games because everyone has different emotional levels and if they are really gamblers they will continue to do these activities without any reason to stop.
For example, fans of sports betting, especially football, currently there is fairly long season break, there are no interesting matches except for few special competitions.
I sure they will play other casino games to satisfy their desire to gamble, plus special competitions are not available every season and this is what always makes it difficult for gamblers to stop.
For those gamblers who really like games, they will always bet and play at any time, what more, the game will create curious effect and also make it easy to lose the gambler focus on setting limits and control.
After all, almost all casino games have percentage of gamblers who really enjoy them, there will always be those who come to play and this will never change.
Gamblers, they gotta gamble. Its in their blood. Yes, they find other methods to get their addiction when sports season slows. Casinos, internet gaming, etc. Its not simply the sport. The thrill, risk, and excitement matter.
Your "curious effect" is huge. New and interesting things attract people. Games are meant to hook you. People, thats business.
We must act wisely. We must teach responsible gambling. Not everyone gambles big. Fun is what most people crave. Give them the means to appreciate it without losing their shirts. Lets teach, equip, and limit them. We cant stop people from gambling, but we can help them do it right.