Science

Had an employer that tried to do that. Sold hemp clothing and said it was basically weed.

Different genetics. Same species, different varieties. Rather like confusing a newfie, a doberman, and a toy chihuahua. Same species. But you don't sic a toy chihuahua on a full-sized German shepherd, or buy a carrier for a newfie based on the size of a toy chihuahua. (
Both are bloody in the execution.)

We've differentiated the terms, it's a useful distinction. Few want rope made of sinsemilla, few want to smoke hemp rope.