To make it look better and to push up the price.

Your dealer is a cock, so dont buy from him again, or TELL him to get you weed that is smokeable and NOT bullshit.

Weed isnt normally laced though, so you were just unlucky.

Sadly lacing drugs is common, well, hard drugs anyway. Now sadly, it's happening with weed too. Just keep your eye out, and if it looks, smells, tastes or smokes dodgy dont risk it.