Yes, that's true, the casino won't make someone addicted to gambling but it's ones own actions that either make them addicts or not. Those who gamble a lot often end up as addicts and those who gamble in moderate way doesn't get addicted at all. That's why one should learn about gambling responsibility so he/she won't get addicted to it.
Gambling addiction can't actually be a general effect on online gamblers . Gambling either offline or online doesn't really tell if a gambler would become an addict or not. Gambling addiction gradually grows from a result of over pilled bad and unhealthy gambling habits and routines. Even before this digital age where gambling online became a thing , people used to gamble only offline before in traditional casinos and back then , there were both addicts and non addict gamblers.
Similarly today , the online gambling space to me brought more of like a flexible environment and method for gamblers to still enjoy their gambling activities anywhere and any time. Still that isn't an excuse to grow an addiction.
Your right. The convenience alone and access to gambling anytime or anywhere have made it a lot easier for gamblers to gamble with ease and it is not a cause of addiction. Addiction is on an individual basis, it has nothing to do with the availability to gamble. In an online casino, it is easier to manage your betting history which can help a gambler keep track of his gambling activities so that he won't get addicted but in an offline casino you keep betting and betting without any recorded history of gambling and before you know you keep getting addicted.