There's two kinds of addiction, physical and mental. Nicotine is probably the most addictive substance in terms of physical addiction (more so than heroin, according to Imperial College London). So comparing the physical addiction to nicotine with a mental addiction to cannabis will never be equivalent. However you can have a mental addiction to anything, even without a chemical dependency - gambling addictions are probably the simplest example. As such you most definitely can have a cannabis addiction, just like you can be addicted to porn, TV, internet or whatever.

It's a habit, and one that you want to do. You might not feel like you need to do it, but it's a strong want. The harm comes if you pursue the habit to the detriment of other things.

It also doesn't help that the clinical terminology is kind of the wrong way around. In clinical terms, "addiction" refers to the physical part, while "dependency" refers to the mental part. This doesn't sit well with me, as "addiction" has negative connotations while "dependency" is more neutral (a child is a dependent of their parents, and this is fine). And yet we still have a gambling "addiction" which doesn't really have any physical element.

But yeah, people can and often are addicted to lots of things. Any habit can potentially be considered an addiction.