please enlighten me.

Shit, when did word filters come back?

My muscles actually just don't bulk. They're super solid, they just don't look impressive.

lift heavier weights with a lower rep. Between 8-12 reps.

Believe me, I have. I've done everything you're supposed to do to bulk up. Some people just don't have that body type. If I ate a ton of protein and such, I'd be able to bulk, but nowhere near as much as somebody who ate the same amount with a better body type. But I actually normally lifted heavy weights, low reps for strength building anyway.

Plus, I actually like being slim but strong.

Except it is an addictive and unsafe drug.

The chemicals in and of themselves may not be addictive, but the euphoria is. You want to feel that sense of total calmness and happiness again.
And it is dangerous. You're still inhaling smoke, you're still fucking with your body.
And it truly is, in many cases, a gateway drug. For people who take a lot of marijuana, it can lose it's effect, they want to chase the first high. They might start taking more potent stuff, and so on and so forth.

No shit if it feels good you want to do it again. By your logic my morning shit is an addictive activity.

In a small way, yes.

But I'm talking more about the chemicals within it you get the mental addiction to, not just simple anal pleasure.