Tone polls! Like Chuck said the beauty of tone poles is anyone can build a course for virtually no cost. That is more powerful than it sounds. It means wherever you go, anywhere in the world, you can still play disc golf, and better yet introduce it to others.
Another big benefit others have said is the purity. Their is no chain out. Their is no, "through the chains" ace. You either hit the damn thing or you don't and you never hear people complain about "oh I got robbed".
Don't get me wrong I love the sound and sights of hitting chains but I will always have a special place in my heart for tone polls. Tone polls single handily launched me into disc golf, and additionally have been a HUGE part of the Southern Oregon (rouge valley) disc golf scene. Medford and Ashland, Oregon have an awesome tone pole course for every season, ranging from epic to fun. The area (couple hundred thousand people strong) had their only 9 hole course pulled due to complaining neighbors and due to a lack of organization have not been able to get more baskets in the ground. That though has not kept them from enjoying public lands and discing at (in order of importance) - Shale City (Frog Creek), Emigrant Lake, Forrest Creek, Lost Meadow, and finally lonely Cougar Ridge (BLM put up a get to keep 4 Wheelers out, they don't mind the discers)
It's encouraging too when you see a tone course sit well with land managers. Emigrant lake is a great example. By spreading the word to keep the place clean, and maybe a few well placed messages or signs, the managers seem to realize that discers are maybe even a good thing for the land, and in that case a tone course actually opened a dialogue about a potential permanent course.