The main benefit, for me, is the fact that hiking poles take some of the strain off of your legs and put it on your arms, which can be strained at no cost to your safety while in the woods. At first glance, this seems like mainly a benefit for older, fatter, or generally more out-of-shape hikers; however, even fit hikers can benefit from using poles if the goal is to maximize the number of miles hiked in a day. Hiking poles can help fit hikers to travel a little faster and without tiring as quickly, resulting in more miles hiked for the same strain on your legs and feet, and since that's all you have out in the woods to get you back home, it's always a good idea to minimize the amount of strain you put on them.
If you think about it, it's not just a matter of only certain people needing them, or of others benefiting from them only sometimes. If you can prove to yourself that they help you hike, there's no reason not to bring them on every hiking trip.
I'd also second everything listed in this post:
>>444621 and elaborate that hiking poles don't just "give you more options" for your shelter, but they allow you to carry a much lighter shelter (the hiking poles take the place of tent poles), thus saving on overall pack weight, and further contributing to reducing strain on your legs and allowing you to hiker farther for the same energy output.
