It's quite simple to know how the online casino's and sports betting sites target their audience using this forum for an example, we have a community here in the forum that's here for a common purpose bitcoin/cryptocurrency which explicitly says it all that any casino or gambling sites that makes use of crypto for it's deposit would target a crypto community like the bitcoin talk for audience.

Another element is that of on land based casinos and sport betting companies their agents mostly target densely locations occupied by low income earners and poor people as it is believe that poor people take gambling as a possible means of escaping poverty as they may get lucky to have a big win that can change their life. And this mentality keep attracting them to gamble without season which indirectly puts the gambling companies in constant  profit. Etc.