The reason for this is that there are obvious problems with only supplying the original date. Most older texts have been edited (or translated) a number of times and therefore are “different” depending on what “reprint” you have. And some of the old and very famous magnum opi were originally published in multiple editions by the original author, each with a number of changes.

Also, for most reprints before the digital age the text was typeset anew for each printed edition, thereby totally screwing up page references: page 47 in a certain reprint edition may be 48 or 63 or 26 in another.

I like Peter’s suggestion to use
Smith, Adam. 1776. An Inquiry Into the Nature and Causes of the Wealth of Nations. Indianapolis: Liberty Fund, 1981.

The problem is to get EndNote (or other reference manager software) to show this.