Convenience, mainly. If I'm given a choice between purchasing and using system compatible adventures vs. non-system compatible adventures, I'm much more likely to go with the system compatible adventures. It's just easier.
That goes without saying, of course. But what I was trying to get at is that incompatibility isn't as big a deal as many make it out to be; furthermore, I would guess that most that cry foul with "I wasted millions of dollars on game books that are now unusable" are experienced DMs that have little problem eyeball-converting.
(As a side point, there's more to adventure compatibility than just the crunch. Sometimes the design approach of the adventures is different for various systems.)
True. I've had this conversation with someone here before and my view boiled down to the idea that I think it depends upon how comfortable an individual DM is with ad hocking and fiating. I do it all the time, so don't mind winging it with regards to rules conversions (as long as I have most of the leg-work done before the session, if only in terms of printing out Monster Builder sheets).
My original post said I'm more likely to accept new editions that retain broad system compatibility with what has gone before (i.e., they're the "same game" in that sense). The "adventure test" is a way of evaluating that.
Fair enough. Speaking for myself, I'm more likely to accept new editions if they are good and offer something innovative and fresh to the D&D experience, while still retaining enough of the core elements of the game to remain "D&Dish."
I have wondered who the target market of a new edition truly is. 3e certainly had lapsed D&Ders in mind - I know I bought in heavily as I left the fold in early 2e. 4e seemed to have a different target group (some aspects to kids what kids see as fantasy these days, some to 2e diehards). Was the hope that the name would carry long enough to get teens/college age people hooked and then "treadmill" them with product? I have also wondered if the long-term approach is "even/odd" - each even numbered edition looks to cater back to the prior even number edition, and odd looks back to odd - you get some carry from the current, pick up a group of lapsed players and they bring in new players (kids, friends, "get the old gang back together"). So 5e mighty be more 3e-ish to pick up those lapsed players, 6e will reach back to 4e, etc.
Just pure idle speculation, of course.
Not a bad idea but I don't think it is that thought out. While economic considerations are, of course, the bottom line with an umbrella corporation as large as Hasbro watching over the shoulders of WotC game designers, I think we often forget a simple truth: Mike Mearls isn't just trying to manipulate the masses; actually, as the lead designer (which I think he is, if I'm not mistaken) his job is to develop the game, to make the best possible D&D that he can. It is the job of other people to make sure it is economically viable - in conjunction with Mearls, of course. But what we forget is that Mearls is, most likely, primarily interested in developing the game itself. I'm sure he's very aware of economics, but his attention is focused on developing the game itself.
The good news is that one of the things I hear Mearls saying is that he wants to evolve the game in a way that brings new innovations (modularity, the "complexity dial") while retaining/recovering the classic D&D feel.