I carry one because I will and am comfortable with out to a 50 yard shot in the perfect scenario. These scenarios are very rare, however when everything is right I want to know the exact number. Bow speed doesnt much matter really in a hunting setup either, in 3D it may get you an extra x ring or two but in hunting it doesn't in my opinion. I am very confident in my yardage judging ability, however that just isn't enough for me when I am aiming down on a live animal. I have learned from 3D that you must have absolute confidence in the number you picked to really have confidence in your shot. To give you an idea, below are some numbers to look at.

280fps arrow - Judged 47 yards - Actual 50 yards - 3.29" low

310fps arrow - Judged 47 yards - Actual 50 yards - 2.63" low

That's less than 3/4" at 50 yards, how many of us are really good enough to see that 3/4" in drop? Speed doesn't fix that problem, but a rangefinder would. If I don't have the time to pull out the rangefinder and click that animal then I don't have any business shooting at it, it was too rushed of a situation for a 50 yarder.

Now another reason, this a bit more realistic for my setup and the woods I hunt.

270fps arrow - Judged 33 yards - Actual 24 yards - 4.12" high.

Now that is quite possibly a deer you are going to have to chase all night long or may never recover. It's easier for me to just bring the rangefinder and click everything when I first settle into a stand so I know without a doubt how far things are and it helps build my confidence. It also gives me something to do when I am bored, I sit there sometimes and just practice picking numbers. I have 14 treestands on my little 120 acre patch and don't get to hunt all of them in the same year most of the time, so when I sit in a stand I usually don't remember how far everything is, so it helps me to just reassure myself a bit with the rangefinder.