No reason that I can think of. I used Polar Pure during the last third of my 2000 thru, and on every hike thereafter. Started at Springer with an MSR filter. Too slow, heavy (an older model). Switched to a PUR hiker in Damascus. Clogged within two weeks. And I’m kinda lazy. Polar Pure is so quick and easy. So ya hafta wait 20 minutes for the stuff to work. No biggee to me. And I didn’t mind the taste either. I sometimes use Tang or other drink mix. Was later told to add the mix after the 20 minutes are up, but I’d been adding the crystals just after the iodine for nearly three months and hadn’t had a problem. That may be correct, though. Dunno.
Oh, some of the water sources on the A.T. ARE kinda icky. Stagnant, muddy, lotsa floaties. So that’s the only issue I can think of. I tried to avoid those as much as possible – as does everyone, I guess – but sometime there’s no choice. Soooo, I also now carry a Bottom’s Up Filter and water bottle in one. Has a little cup on the bottom you can pull off to help scoop-n-fill. Then you just sqeeeeeeze the water into your facial orifice, as it gets purified on the way out of the bottle. Velly simple, velly easy, and the floaties and ickies get left behind. A nice combo with the P Pure.
Ramkitten