Among the many things it does, repetition works very well for getting people to sing, so it appears in many forms. Song choruses are probably the best known. Other songs repeat the bridge and the last verse as a form of conclusion, and yet others repeat the first verse. "Zipper" songs follow an outline that changes only a few words in every verse - such songs make it easy for people to make up their own verses.
And some verses are used in a variety of songs.

-Joe-