I've never lived in a town that uses one for a curfew siren, but I've found it fairly odd to use one for such especially for a late curfew like 10pm.
Another odd/interesting use was that at one time the Wisconsin Central yards Roundhouse in North Fond du Lac used their STH-10 as a alarm to alert anybody in the vicinity that the roundhouse turntable was going to start moving. I had to darn near change my underpants the first time I went trainspotting near the roundhouse at night when I was young (pre 9/11)