This idea of certain flights being leisure and others business is absurd - in practice about 99% of all flights are involved either directly or indirectly in optional leisure. A businessman flying out to do a deal on DVD recorders, cars, washing machines is in effect concerned with optional expenditure and is no different to taking a trip to the Costa del Sol.
Name one aircraft use that is not directly or indirectly involved with leisure/optional luxury expenditure? There are very few.
In our society almost all expenditure is optional luxury expenditure.