Because stores use a high quality feed

Yes, obviously, and consumers who are buying such high-end displays should do their best to provide the highest quality source to play back on those displays.

Distance from the display is important, too. On a small TV, you'll be close to it, but resolution won't matter as much.

But from across the room, you want a higher resolution display up to a certain point, or else you'll see large pixels, and that looks terrible.

Personally, going with a 4k TV was a big leap, but the addition of HDR and an OLED display (for black blacks) had the most impact.