Reason(s) for not allowing customer credit?

[DaoDeJing]

Is something legally prohibiting Square from providing customer account credit functionality?

Perhaps doing so would require some special type of banking permit that Square does not wish to obtain? Perhaps just the increased hassle and potential for liability should funds vanish be a point of concern? Or maybe they have an agreement with eCard Systems that prohibits the release of such a feature for a certain length of time? (Since issuing gift cards is a common work-around for lack of this function, I'd imagine implementing it would decrease their profits.)

I don't expect a frank answer, but figured there wasn't much harm in asking.

But I do not believe the delay has anything to do with difficulty of implementation or having a long list of other developments of higher priority. It is hard to imagine a more vital function stores would be needing at this point.