Because the types of moments or compositions that Instagram chooses to focus on are low resolution. 50mp is great for a large print, and Hasselblad sharpness, and 10 lights. But Instagram chooses to offer noise and color filter to everyone with a smartphone, so they can make their salad or dog look cool. I have lots of lenses and I love instagram, because I don't have to worry about pixel peepers and get genuine feedback.