We'll, it's a couple things.
First is that I have big plans for DG, so I'm setting that bar pretty high for myself. I certainly could rush out the game, but I doubt either of us wants that. Besides which, in many ways "released" is merely a label. The beta is very playable, and is gaining polish at a good clip. In the event that the release date slips, all backers, even below the beta access tiers, will get access to the beta so that they can enjoy the game.
Second is that I don't actually intend to launch as late as Sept 2021. In fact, I have every intention of releasing before the end of 2020. But how many KS games actually meet their original launch deadline? As far as I've been able to tell, not many. Nay, hardly any at all.
That's because projections are *really hard* to make in software development. It's something of a universal truism, and the error bars almost always flow in the wrong direction. So I decided to set the projected launch date further out than I otherwise might have in an attempt to bake in those error bars. I feel that I have an obligation to my backers, and I want to do right by each and every one of them...I certainly don't want to accidentally mislead anyone.
And that's why the date is set as far out as it is. With some luck, the game will release sooner. But I can't promise that, so I won't. I know this will probably cost me some sales, but I'd rather lose sales than the alternative here.