How does the setting contribute to the plot in "Witches' Loaves" by O.Henry?

With the setting of a bakery, the encounter of Miss Martha
Meacham and the middle-aged German man is initially one of chance, as well as one that
is brief.  Each day he comes for stale bread which he purchases and then immediately
departs the bakery, so there is little opportunity for Miss Meacham to speak with him. 
For this reason, she contrives the posting of a painting so that the German customer
will notice it and react.  In this way, Miss Meacham may be able to determine if he is
an artist as she has suspected.  The next day when the man enters the bakery, he does,
in fact, comment upon the painting; therefore, Miss Meacham believes that he is a
starving artist. In her sympathy and interest, the baker slips some butter into each
loaf intending a kindness.  But, the irony is that the buttered bread destroys the
German draftsman's drawings, causing him financial ruin.  He returns to the bakery,
cursing the baker.

Clearly, the bakery as the setting
controls the actions of the plot.  Only once each day does the draftsman come, and Miss
Meacham can but guess at what he does in his obvious state of penury.  And, since she
only sees the man briefly each day, she does not get to know him well.  That there can
be the misunderstanding between Miss Meacham and the draftsman is entirely possible
within the setting, and, of course, that she can dash all his hopes for success with her
simple loaves of stale bread is also possible in O. Henry's ironic short
story.