The point is that if you give the $20 to a homeless charity they are going to use it to provide 20 or even 40 meals in places where real homeless congregate. Giving money to panhandlers is vastly less efficient not just because many are scammers but also because you aren't reaching most of the homeless population or an organization that can leverage economies of scale to buy efficiently. The people who hang out at busy intersections with signs, particularly in suburbs where they know many easy marks exist, are not representative of the real population or problem.