Just about everytime I have fallen out of love with a game or genre, I can trace it to one thing......destruction of the fluff (or established canon).
BITD I played a lot of 40k. W40k 3ed and 4ed were my time. I picked up the game in 2001 after playing a solid 3-4 years of DBM (historical Ancients) were there were four army list books containing 300+ armies. All the armies were based on established history (read canon).
My local club, the Wellington Warlords, was big into 40k at the time. It dominated tournaments in New Zealand and Australia and had perhaps 6 of the Top 10 tournament players in Australasia. It was a tough school with a steep learning curve but as a result of playing in that environment you quickly became a very good player.
However the one thing that was important was the established fluff. Third Edition came after the Herohammer and army ally allsorts period of 2nd Edition. I never played but apparently the lists were shite (though largely pre-internet so not as invasive). At the time GW was releasing new codexes for all races - and variant lists in White Dwarf. We had mini-dexes for Dark Angels, Blood Angels, Space Wolves as well as the Armageddon dex, Craftworld Eldar and Ork Clans (WD). Index Astartes articles dropped and the eventual conclusion was CSM Legion rules and Space Marine Chapter Tactics.
This led to armies being highly themed with the established fluff. This was encouraged by GW with their Rogue Trader Tournament system. Woe betide anyone turning up to an event with a list that strayed from fluff. Tactical Marine Squads were 10 men strong and you were TFG if you turned up with a minmaxed 6 man lasplas squad.
With 5th Ed and the rise of net listing that all started to die. The tournament game you read on the net now is very much one of pure efficiency with little or no hat tip to fluff. 2016 saw the rise of the Super Friends list that was designed euphemistically as a force multiplier.
I got out in 5th when we lost Traitor Legions, Eldar Craftworlds, Ork Clans etc. Visiting an event last year where lists were basically Super Friends plus a Knight confirmed to me I hadn't missed much.
In about 2007 I drifted to Warhammer Fantasy and loved the Old World. The fluff was deep and made sense to me. I could invest time in my armies, terrain etc. My love of the Skaven is well-known but pick any of the armies and when I faced it on the table I knew its backstory and for me that's important. At the end of 2014 the End Times arrived and I embraced the story progression - if not necessarily all the rules. However we did see then how when the backstory broke down things got silly on the table in unintended ways.....Host of the Eternity King anyone? I think this was the precursor to "Super Friends". Well we know the End Times didn't end well and the established canon was destroyed along with the Old World. Again I jumped.
The last year or so has been an interesting time for me gaming wise. I've been playing Kings of War and really enjoy the game. But I have no investment in the fluff. It means nothing to me and I don't feel any ownership. Of course this is understandable where the game doesn't have the benefit of 30+ years of backstory. That is why I am very interested to see what 2017 brings. This weekend is International Campaign Day where two US gamers have created a global linked game structure across 12 countries with the outcome in one area influencing the events in another. Mantic also have their Summer Global Campaign Event which is billed as advancing and broadening the backstory. For me the development of a narrative behind the game is the most important improvement Mantic could make for Kings of War. I want to know more about what drives my Ratkin or what grudges/allegiances my Herd have. At the moment I have little buy-in to their backstory other than the former are rat-like and the second are fast. It would be great to have that built upon. And no fan fiction doesn't do it for me.
Mantic have a real opportunity here as Age of Sigmar largely destroyed the established backstory and GW have started from scratch. Yes, they have significantly greater resources than Mantic but that shouldn't deter Mantic from their endeavour. The other Fantasy contender, The Ninth Age, is in a funny position. We all know that it is next edition Warhammer regardless of their protestations but they are effectively stuck in time. Yes, the names have changed, yes they are writing fan fiction but they do not have the resources of a company behind them and that will ultimately hurt them. To succeed it needs to be monetised and that will be the beginning of the end for them.
So this has been a longwinded treatise saying that IMO you need to have narrative fluff and you need to have an eye on the story progression to get my hobby dollar. I'm sure other people have different triggers but history has shown that a strong canon gets investment from players - and especially those players where tournaments are not the be-all and end-all. GW has recognised this and realise you must balance competitive issues versus narrative (e.g. the backtrack on AoS points). This year has seen them make 40k releases that are driven by fluff - Genestealer Cult, the Fall of Cadia and especially Traitor Legions.
I'm hoping Mantic will grow the narrative side of KoW as I'm sure that is the key to future growth