We see this fairly often with our Search and Rescue "subjects". It's a combination of target fixation and that hope that this is just a rough patch and the trail will open up again "just around the corner".
Just a couple weeks ago, we located and brought back a middle-aged couple who went out on an afternoon e-bike ride in the backcountry. They found a nice 20 mile loop of singletrack and forest service road on the AllTrails app and headed out with minimal clothing or supplies. The trail was beautifully maintained, taking switchbacks down from the ridge into the valley and to a campsite, but beyond there, it was in disrepair, overgrown, washouts, treefall, etc. But they kept pushing on - the loop they had planned was on the map after all. But no, the second half probably hadn't been maintained much less traveled on in 5+10 years and soon it completely petered out for them and they were left, deep in a valley, at night, with the temperature dropping, in shorts, with no water or food (he was a diabetic and they both had heart conditions).
My team dropped in from the far side which was closer to their location but even with multiple maps and satellite imagery could not locate the trail for any significant stretch which led to several miles of late-night bushwhacking down steep hillsides to reach them. Once checked out, provided with warm clothing, food, and water we all hiked out the way they came in which took the rest of the night and we reemerged at the trailhead at dawn. They were very lucky that due to the orientation of the canyon, they had cellphone coverage.
Happens fairly often.
Another one, last summer, was a guy who set out on a 3 day, 40 mile loop, got sick the very first day and instead of turning back, kept pushing on and was found severely dehydrated and still ill 36 hours after he was supposed to have completed his hike. He spent several days in the hospital...