I mean, sketching them really makes you learn the star patterns in a way a photo doesn't. Like, I could never remember the difference between Cassiopeia and Cepheus until I had to draw the lines myself. The phone pic is just a quick record, but my hand trying to connect those dots is what stuck in my brain. Maybe it's just me but the easy way doesn't always teach you as much.
Drawing constellations by hand is like dial-up internet. Slow, frustrating, but by God you learn patience. @casey393 betting your phone battery dies halfway through the sketch too. My lines always look like a spider took a nap on the page.