Indeed, you might not.
It might be a design optimization to offload treater duty and fuel consumption. It might help to some degree with separation / treating, or avoid the complications you might otherwise have with adding a demulsifier if your emulsion is difficult, but lots of plants and batteries don't preheat the feed and they work fine. The Process Engineer (if any were involved) would be in the best position to explain the rationale.
Regards,
SNORGY.