My car is leased due to other PH work I've got.
A new car every three years - you'll always have the latest model, especially in terms of fuel efficiency and legislation.
Anything goes wrong is fixed under warranty (which is unlikely anyway on a new car)
I can negotiate higher fares from potential customers/other companies due to a new car.
Maintenance costs are kept to a minimum, usually associated with higher mileage cars.
No wear and tear items need replacing during the first few months of ownership (main ones being tyres and brakes).
Simply hand the car back at the end of the term - no need to deal with the hassle of trying to sell it.
Tax efficient - the entire cost, can be offset against your earnings for income tax.
You'll have to replace your car every few years anyway (due to wear and tear, and/or ongoing legislation), so may as well get a new one every time.