Cannabis is one of the most relaxing, euphoric, mood lifting and generally comforting drugs that I have used. There are no repercussive after-effects like hangovers or serotonin depletion that prevents me from using it regularly.
It has all the hallmarks of an addictive drug, yet somehow, a lot of people aren't affected by it.
When I have been smoking weed regularly, and that use abruptly ceases, I experience withdrawal symptoms like with any other drug; a complete reversal of the drug's effects: Loss of appetite, discomfort, insomnia, low mood, hypomania, wild dreams.. I once hallucinated a bong in my hand and watched it disappear as I went to smoke it.
I try to limit my use as it is most effective with low tolerance, but I benefit from it a great deal, so it is difficult to get the balance right.
Anyone who thinks it's okay to say that something doesn't happen just because it doesn't happen to them.. or that's no big deal, just because it's not a big deal to them usually sounds like a bit of a cunt. The hypocrisy is the worst. "You think weed is bad? Try withdrawing from a gram a day of my shit drug". That's not how it works. The effect that someone gets from one drug is not relative to the effect someone else gets from a completely different drug.
TL;DR: if you don't experience any withdrawal effects from weed, that's great, but some people do.