I wouldn't be surprised if a majority of those buying FS are mostly done with it after a few weeks/months. And then, after weeks of not playing, they may start it up again just to kill some time. Maybe they find some new interesting mod, and play around a bit with it. Then they forget about it again and play other games that has been released. That's how I see a lot of people I know treat most of their computer games. Those players are bored and 'finished' with a game well before it is even six months old. They don't care one bit about our FS19 complaints regarding realistic farming operations or weird graphics/sound or half-broken terraforming features. They won't even try to get some help if they have issues. They just shrugs and move on. Hardly any of those care about any FS forum, so we may not think they are for real. But I guess they are the ones bringing in the big money for GIANTS. So don't count on GIANTS caring one bit about people still playing FS17 or why they do it.
As BulletBill wrote, even minor updates along the way in constant-update kind of cycle will eventually break things that requires mods to be fixed. And then we need the original modders to be there months after months, year after year, willing to fix their mod if it breaks. With a more traditional cycle with big new versions every 2-3 years, I guess most mods released after the first major bugs been ironed out will continue to work for the rest of the versions lifetime.
<-- FS17 on an iMac 27" playing Lone Oak Farm and The Western Shore -->