It's called killing. Hunt long enough and kill enough deer and you will eventually make a shot regardless of whether you shoot shoulder, neck, lung, heart, or head, that you will cause the animal to suffer because for whatever reason you missed your mark. . . .it happens.
Thats frankly one of the reasons I quit hunting with dogs and shotguns . . .I couldn't consistently humanely take deer as I was frequently hitting them wrong or missing all together, who knows?
Hanging in a tree, the animal usually never knows your there and you can wait for a good shot opportunity. A lot comes with experiance watching deer and how they move, time spent shooting, and know your terrain.
Now for my "old man" statement . . .I'm dang near 60 yrs old and have been harvesting deer 50 of those yrs. I don't even know how many I've taken. Can count on one hand the number I've head shot. Since I've been still hunting (about 30 yrs) I've averaged 5 deer a yr . . . .every one of I gave the respect of every effort to make a well placed shot, recovery, and immediate processing. I still learn something everyday in the woods but I know what my skill level is and my limitations.