Yes there is an individual factor, some people have more willpower than others. But if people get addicted then the substance is addictive. As it is widespread then it can be attributed to a chemical factor. Not just a psychological one.
"God is dead" - Friedrich Nietzsche
"Faith is what you have in things that DON'T exist. - Homer J. Simpson
"Faith is what you have in things that DON'T exist. - Homer J. Simpson