Because carto tanks are pretty and I can get them in girly colors. =P Why can't I just stick to my cartotanks that don't leak, where the coils always wet, the taste is good, that I don't have to do anything for aside from hit the fire button.... Also, I need lots of toppers as I switch juices all day long an I don't care to find an all day vape. I like variety, and I like my coils to each have their own, dedicated flavor and never contaminated with the last flavor I vaped.