I think the reason why you'll find most people practicing out to those distances is: 1) It's fun, and (2) It makes 20-yard shots seem like "slam-dunks".

I would have to question anyone that would consider shooting at any live big-game animal in North America much past 45 yards or so... and maybe even a touch closer than that. My reasoning is simple: Even if the animal is calm and undisturbed, an animal can take at least one if not two steps at an alarmingly quick rate when it decides to simply walk a bit forward -- even when unaware ofan arrow speeding its way. A couple feet later, and that for-sure heart shot has just become a marginal hit at best, and may lead to hours and hours of tracking.

Even though I'm sure there are many here who are confident in nailing a grapefruit at 50 or 60 yards, I like the way I heard it put this way best: Bowhunting isn't about seeing from how far away you can take an animal, but from how close.