Ten plus years ago when I first started playing Aces High it was because I had my desktop computer leftover from college.  That thing is long gone and since then I've owned two MacBooks, a couple iPads and iPhones.  The desktop is not nearly as common as it was in the early 2000's and regardless of advertising I have to think that is a major reason player count is down.  I'd like to comeback but that would require buying or building a computer that I would only use for gaming and I'm just not sure I want to do that.
Anyways I sure hope the game returns to the old numbers.