It's certainly a possibility.  Particularly since 1. It's common for one of the spouses to handle investing matters, usually the husband; 2. It's well documented that men and women approach investing quite differently, with women having greater risk aversion (I don't know how all of this works for same-sex couples).  The stereotypical pattern looks something like: husband handles investments, allocates rather aggressively during bull market; bear market hits, portfolio losses make wife upset, makes husband adjust portfolio to be much more conservative near market bottom.  So the couple ends up allocating very inefficiently over the market cycle.  Note that this is pretty much the same dynamic most fund managers face - shareholders are prone to withdraw assets during the periods of greatest opportunity and vice versa.  

Best,
Oildog