I wonder if you guys who think this was just a "mistake" would be so forgiving if it was your house he crashed on.
Fuel is an integral part of a powered flying machine. Most aircraft will fly with quite large portions of the airframe missing (ie parts of wings, fin or tailplane), but no one in there right mind would take off in one in that state. So why accept a shortage of fuel?
As for the argument of inaccurate fuel gauges:
If weight and balance or performance is not critical, fill it up. If it is, drain the tanks and fill it accutately (time consuming, but there is never a time constraint in GA, not where risking your life is concerned).