Not proved is relevant and acceptable conclusion because otherwise, a forced conclusion, especially in the absence of better facts/evidence, will cause injustice to either of the parties. Besides, we've an adversarial system & not inquisitorial. The courts are bound to adjudicate on the basis of the best possible evidence/facts available.
'NOT PROVED' can be a conclusion owing to the fact that has been discussed with respect to waiting for the best evidence. It has been discussed that it is impractical to wait for good evidence. A fact cannot be proved when there is no evidence to prove or disapprove. If the court does not come to a conclusion, it will be a never-ending trial.
The definition 'not proved' given in most of the bare act of lndian Evidence Act is incorrect. It is correct if we say 'a fact is said to be not proved when the fact is not proved not disproved' and not said to be proved or not disproved'