It’s generally wise to be prepared when heading into unfamiliar territory, and a GPS can provide protection if conditions turn out to be less than ideal. Issues like bad weather reducing visibility, washed out trails, poorly marked trails (worse if combined with poor visibility). Fog, rain, or snow can all be problematic and make a trail finding task that would be easy in good conditions, turn into a situation where one can easily get completely lost.
We have all more than once taken a “short cut” after descending a climb, following what was initially a pretty good trail, only to have the trail peter out and end up in an epic bushwhack back to the car in the dark. A GPS can save you on early-season backpacking trips where snow might hide an otherwise obvious trail.