Why/when to use USES=desktop-file-utils.mk ?

[Gerald Pfeifer]

Hi there,

it was suggested to me (PR/195903, thanks Dmitri!) that I add
  USES=desktop-file-utils.mk
to the emulators/wine ports, and I'll do that later today.

That said, I read Mk/Uses/desktop-file-utils.mk itself as well as
https://www.freebsd.org/doc/en_US.ISO8859-1/books/porters-handbook/uses.html
and while I may have an intuition, neither really helped me understand
why -- and especially _when_ -- one should use this.

Can you please advise?  (And ideally update the documentation along
the way?)

Thanks,
Gerald