Only half kidding. In the UK, as a contractor/freelancer, it's easier to make the case that your company is a going concern in its own right (rather than a simple tax-avoidance shell) if you have projects other than the main one you're working on for a client. Particularly if you're working on-location for extended periods.
I also want to learn new things, build up a portfolio and eventually start a software company. So I guess all of the above?