Finding a minimum cut for an (s-t) flow: why not just cut the start/end edges?

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Most examples I've seen involve cuts snaking through graphs picking off various edges.

My question is why not simply do a cut either involved the edges leaving the source or the edges entering the sink?

Max-flow min-cut theorem says the maximum flow is equal to the minimum cut so surely either of these two cuts satisfies the conditions for a minimum cut?