For he first fifty years of the BSA, adults could earn Eagle along with their sons. Bryan's Blog posted Some clippings of how that played out:
http://blog.scoutingmagazine.org/2015/07/02/10-times-history-adults-earned-eagle-scout-award/
I've heard a few reasons why this practice ended. The position of responsibility requirements were added; however, adults hold official and unofficial positions in a troop. Likewise, leading a service project (also a novel requirement at the time) would be as challenging for many adults. One respondent to the blog cited a 1972 handbook: "it would be unfai