I always found it useful for giving mx a heads up about a broken airplane I was bringing their way. It gives them lead time to sort out the problem and arrange for parts to get started that way.
Another good aspect is allowing the company to contact you to let you know about wx, atc issues or whatever else was going to affect your flight giving you time to sort things out ahead of time. Also, when things went downhill and you knew you weren't going to end up at the destination as planned it gave the company some input as to where they really wanted the airplane instead of just a legal alternate.
The downside was when that old favorite showed up, 'contact crew scheduling, please acknowledge'. Somehow that always showed up the last leg of a trip before days off. Go figure.