How is this any different that starting a legal weed shop that also happens to sell to people that are addicted to it? I knew plenty of people when I was young

How is this any different that starting a legal weed shop that also happens to sell to people that are addicted to it? I knew plenty of people when I was younger that would spend so much in weed every month that they couldn't make rent. If we are going to support legalizing drugs (which means the choice to destroy your life), we also need to support legalized gambling.