In my opinion, not all the verses to all the hymns are appropriate to all the occasions.
A case in point might be “Eternal Father, Strong to Save (Navy Hymn)”. It has more verses than “99 Bottles of Beer On The Wall” and not every branch of service and/ or acitvity needs to “represent” to make it appropriate to the occasion, scripture, and feast. Is it really necessary on an air force base to sing about those in peril on the sea?
Some hymns have seasonal verses, one for Lent, one for Advent, one for Ordinary Time. Why sing the Lent verses during Ordinary Time?
Another good reason is hymns with several translations. I have heard very lovely versions of “Silent Night” in five different languages. It was not necessary to hear all four verses, all the way through, translated from German into English, Spanish, Polish and French. It was better with the first verse in German, second Spanish, third French, fourth Polish, then everybody joining in on the first verse again in English.
This is especially true of hymns translated from Latin. One verse in Latin, one in English, unless it’s a EF Mass or rite.