The 2003 Ford Explorer XLS was the baseline trim in this model line; adding all-wheel drive to the XLS may have increased the cost, but it must have seemed worth it to the buyers who selected this option.  However, there was quite a bit of controversy about whether four-wheel drive systems didn't actually yield more control of a midsize SUV like the '03 Ford Explorer, and Ford discontinued the all-wheel drive option on the Explorer in 2005.