Not surprising, especially since (according to various studios) most games are never finished by a significant percentage of those who've installed them. For example, I've had Deus Ex HR & Batman Arkham City since before Xmas and have yet to complete either of them. Not that I didn't like them, I just left them alone for a while and never got back to them. I've been playing Skyrim for several weeks now and I fully expect that I'll uninstall it before getting anywhere near finishing the rebellion quest line.
With the ME3 ending fiasco, it shouldn't be a shock that a lot of those that bought the game only played it to a certain point before quitting. I wonder how many of them just watched it on youtube?