Because I've found they replace just as precisely as when both rings are as far forward as possible, but the rifle usually doesn't require a shot to "settle in" are the scope's replaced, as they sometimes do even when the scope's pushed forward while retightening the mounts.
Either way works, but I suspect what sometimes happens with both rings pressing forward is we don't have as much pressure on them while tightening as we think. Eventually I decided to try spacing the rings as far apart as possible, and it seems to be the most consistent method.
