This is true. However, this is taken care of by basic taxes and welfare. (Judging by my experience with HN discussions, this usually leads to talking about how US doesn't have enough welfare net; I want to point out that this is not the topic of the conversation).

So let me ask you a question — when we discuss this "back" direction, would you include someone who's been living on this welfare net for all of this life in it? Someone who purposefully declined to contribute anything to the society? The very phrase "to give back" implies that we're giving to someone who gave us something before — and this hypothetical Joe sure as hell didn't give anything to us. *

Since my question is purely rhetorical, let me answer to it to get to the point. I don't think that you would include him in "giving back". And yet, we keep him (or at least, me and you agree that we should try) fed and alive to some degree.

So, this whole notion about "giving back" is something different from keeping this hypothetical Joe alive. What is it, exactly?

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* This paragraph may sound similar to typical right-wing propaganda about lazy people living on welfare. However, it is only a hypothetical example to prove a point. I'm not making any statements about real people in it.