Physical gambling is confined to a physical location (like a casino or a sports betting bar), so people have to go there to be harmed. It's bad, but it requires someone to spend time getting there (and if the victim has a family/friends they might ask where they're headed/intervene in some way) and there is a limit to the amount of people who can be there at once. With digital gambling, anyone can spend any amount of money, anywhere, anytime, with no oversight (however little it might be in a physical location). The harm is magnified immensely.