That's because they're now on something like v4 (v3? v5?) of most of the technology behind the game. They keep reworking everything over and over and over agai

That's because they're now on something like v4 (v3? v5?) of most of the technology behind the game. They keep reworking everything over and over and over again. And at this point why wouldn't they? Their customers have pretty much shown they'll continue to pay for all of that rework in perpetuity.