I've used them a lot, including many times before I knew that's what I was doing. Primarily, I move from one to another to differentiate sections (A, B, C) so that a verse, say, may be in C, but the chorus in Am. But just to borrow a chord from the relative major/minor key works musically even without changing the tonal center. It depends on how long you hang there.

BIAB 2021 Audiophile. Windows 10 64bit. Songwriter, lyricist, composer(?) loving all styles. Some pre-BIAB music from Farfetched Tangmo Band's first CD. https://alonetone.com/tangmo/playlists/close-to-the-ground