There isn't a monolithic thing you take called 'weed'...Most people completely fail to understand this...even the ones who take it. So if you see all your friends who smoke a sleep inducing chemical concoction they call 'weed' of course you will think they are lazy, unmotivated, dozy, etc.

The reality is there are a plethora of effects it can have for people some beneficial some not depending on the person and what they want to do.