Now is the beggar providing a service or a good? Debatable. On the surface, no, they are living off the benefits of others and not contributing back.
However, when that beggar spends the money, they are then contributing to society. Even if it is just for alcohol or drugs. Money is going back into society in another arena.
Additionally you could say that the beggar is providing a moral service. If I give money to a beggar, generally I'll feel better about it. It's similar to giving money to a charity except that I know the person needing the help is getting 100% of the money.