An interim service helps to maintain the performance and efficiency of your vehicle. Regular maintenance is important for prolonging the lifespan of a vehicle and reducing the need for repairs. Because of this, vehicles with a regular service history can often be deemed more desirable by used vehicle buyers and therefore they may retain a higher resale value.
This type of service is typically required if you're vehicle covers a high amount of mileage annually (the UK national average is approx. 8,000 miles per year) but as every vehicle is different, you should always refer to your manufacturer's handbook for guidance on what type of service your vehicle requires.