WHY IS WEED ILLEGAL AND SALVIA LEGAL?

I have smoked weed for 10 + yrs. and it has helped me with MANY issues. like cramps, nausea, stress. and my ADD. there are a few more but y waste my breath. i have used SALVIA over 5 times..it is a SURREAL experience, BUT if someone were to use it while driving it WOULD cause an accident. but smokin a blunt while driving will not effect your abilities, and u wont be trippin'. wtf is up wit the GOV. ?