since for because
Since as a reason, not only as a time.
Since may mean because: Since the gate jammed, we waited. Recast when since could also mean from that time: Since the shop closed, we have driven farther does not tell whether the close is the reason or the starting point.
Examples
Use Because the shop closed, we drove farther.
Use Since dawn we have waited.
Avoid Since the shop closed, we drove farther. (If you mean the reason.)