Solar still are worth learning to make. Transpiration bags are better but if there are no trees or bushes then what ya gonna do. solar tills can be used in areas and during seasons where transpiration bags are not feasable or you don't have enough plastic to make one. As far as not being worth making I have used them in training and if you make more than one they can and have produced enough water to sustain life, consider which is better a small amount of water or none.
Edit to my original
Be careful what plants you use with the transpiration bags on some plants can alter the taste and the can transfer various toxins that can affect you in bad was, the same can be true of solar still if plant matter is used.