Time, consistent practice and acquired skill from said practice, and limited range. Those are the reasons I have hung up the trad bow.
I shot a reflex/deflex longbow for about 3 or 4 years, and had some success -- whitetail doe, small whitetail buck, even smaller antelope buck. It was a lot of fun, and a good buddy also shot trad (recurve) so we hunted together and had similar effective ranges, etc.
But, looking back, I recall at least 4 or 5 elk hunts throughout the seasons where I had to pass on shots on good bulls that were called in to about 35-40 yards and hung up. No shot I felt comfortable with. My range was 20-30, preferably 20-25. With a compound, it would have a been a different story. So I think the real issue is a reluctance due to limited range, which can equate to reduced shot opportunity. That is a hard fact. I don't have weeks and weeks to hunt, so I am going to maximize my chances, and with that, I switched back to a compound. But, I still have that longbow and a sweet ILF recurve that is really fun to shoot. I may take it out for a whitetail doe hunt out of a stand, but when elk/bear/antelope tags are in my pocket, the compound comes along. It all boils down to a passion for that kind of weapon and hunting style. It is a really cool way to hunt, and I enjoy everything about a trad bow, but I also know what increases my shot opportunities during a season with limited time...
If you are even remotely curious, try it. Don't be some 90 year old sitting in a wheelchair wishing you had had given it a good solid try back when you still could. Asking "What if..." is the worst question to ask yourself. And if you absolutely suck at it, guess what -- that compound will welcome you back faster than a poker table in Vegas.