A guide is not always indispensable. You need a guide when you don’t know which river to fish, when to fish it, and even if you know which river you want to go, which stretch of it is more productive.
A guide brings you directly to the best pools, in parts of the river he often only knows. The guide will give you the right fly for that special situation, telling you how to cast and other tricks in order to catch even difficult trouts or graylings.
The guide will not fish, he is there to make his clients fish.
He will advise you to the best technique to use, depending on water levels, hatches and river morphology. Beeing guided doesn’t mean only looking forward to catch fish, it also means to compare our skills with someone else and maybe to learn something new.