We used them to develop balance and blend. Unison, tone cluster, unison, tone cluster, etc. Step out of the balance of the ensemble and then get back in it upon resolution. Not necessarily space chords as the staff didn't necessarily agree with how they are taught and used in some groups, but more tone clusters.
Favorite staff quote in regards to space chords (which may need to be edited):
"Space chords are musical m**********n. They simply exist to get the guy in front of you off."