Because the Dirty Devil sucks. Route is easy apart from one very exposed 20ft long slickrock scramble.
The Dirty Devil sucks, at least it did for us. The river was flowing high (high thighs at the choicest crossings) and we found abundant evidence of an enormous flood event from probably a week before. This meant the river terraces had been completely reamed, the thick late summer vegetation was unpleasant to bushwhack through, and quicksand/shin deep mud was overabundant. Travel was painfully slow.
With still another 1.5 miles to go to reach Posion Spring Canyon, Ryan spotted an intriguing set of animal trails disappearing at the base of the shortest part of the cliff bounding the Dirty Devil Canyon. After consulting our map, we decided that if we could get up that cliff we should have no trouble finding an easy route into Posion Spring Canyon. So we climbed the mudrock scree slope high up to the base of the topmost 20–30 ft of the sandstone cliff. Gaining the cliff requires following a ledge/crack of sorts diagonally up to the right. For about 20 ft this mild climb is extremely exposed (be very careful), but there are decent handholds along the ledge and adequate footing. We cleaned a few loose rocks off this surface suggesting it has only been used as a game trail previously. From here follow a drainage up to reach an old uranium mining road. You well see the remnants of a wood building and a green metal bench someone went through considerable trouble to bring here. We dropped our packs and followed the washed-out road up to the mines for a quick look. There is an old shack and some mining artifacts left just inside the most extensive tunnel. We only went in a short distance (for fear of radon accumulations), but enjoyed seeing petrified wood in the walls and ceilings, partially replaced by yellow uranium minerals. Back at our packs we followed the road around the corner and then bombed down the hill through all the road switchbacks to arrive at the floor of Poison Spring Canyon (taking the entire road is about a mile longer).
This route leaves the HDT at about Section 4 Mile 19.4 (Mile 174.1) and rejoins the HDT at about Section 4 Mile 21.3 (Mile 176). This route is 1.4 miles long (excluding a pack-free detour to the uranium mines), 0.5 miles shorter than the HDT (though with an extra 300 ft elevation gain). If you have had enough of the Dirty Devil and can stomach a little exposure, this could be your route.
Ryan "Tuna Helper" Weidert