You seem to be under the impression that anyone here has an obligation to make sure that you're adequately convinced.

You clearly won't believe that most drug transactions are done in cash unless you see incontrovertible evidence. That's fine. But no-one cares, so I don't know why you expect demands for a source to be met.

If this was an even remotely controversial or decisive topic, it's worth providing sources, because they convince not only the person demanding it, but also anyone reading. But in this case, it's such a well-known and obvious fact that there's no such benefit.

You can ask for sources for "the sky is blue" all you want, but I'm happy to just stick my head out the window and go "yep, I'm pretty sure". I'm not too fussed if you still don't believe me.