If we think it is indispensable to name a photo; in fact, it may not be the case.
The name of a photo, of course, has encompassed the idea that the photographer wished to transmit, as sending out a signal. But, the name of a photo can also diminish the imagination of the viewer unavoidably.
It is true that a viewer can also surmise in front of a named photo; but, the thought or supposition would be limited by the name, inevitably.
Say, a photo is entitled “Red Rose”, it would be insensitive, or even unreasonable, for a viewer to surmise it is a black rose…
(I might have more to say about this…)