Why isn't door knob tight to the door?
After thinking to search specifically for Kwikset locks with this issue, I found this video referencing it. Guessing it's an issue with at least some Kwikset knobs. Thanks for the helpful comments. https://youtu.be/skME0j8hsOM
ETA: at least some Kwikset knobs have these two metal nubs or dimples on them. The video's solution was to use a course metal nail file to grind the nubs down to not create the gap. He didn't mention the cut, but I'm assuming at least second-cut.
Isherwood mentioned above that these dimples serve a purpose, and, with enough tightening of the screws, will dimple the door, eliminating the gap. I tried this first, tightening the screws even tighter than I already had them and the gap disappeared, or at least was unnoticeably small.
So both would work, but I'm marking theirs as correct since the dimples are supposed to be a feature.