A few trials should convince you that this simple exercise is of great value.
HALF-BREATH In both singing and speaking, the sustained delivery of long phrases or sentences sometimes makes unusual demands on the breath supply.

It is a law of good singing that every phrase should end with the breath unexhausted.

When the flow of text and music forbid the taking of a full breath, half-breaths must be quietly taken at convenient points.
Instead of letting the whole reservoir of motive power exhaust itself and then completely refill it, we should, by taking these half-breaths, maintain a reserve.

A notable advocate of the use of the half-breath in singing is that past mistress of sustained and smooth delivery, Marcella Sembrich..