Shuttle cross-range Q.

This article about the X-37B:
http://www.theregister.co.uk/2012/12...unch_tomorrow/
reminds me of something I've been meaning to ask.

Much has been made (by some) of the military-mandated cross-
range capability of the STS which (according to some) essentially
crippled the Shuttle as a civilian transport due to the excesssively
expensive and fragile TPS.

The given scenario is always a single polar orbit launched from
and returning to Vandenberg. But why not just launch from, say,
White Sands, and land at Vandenberg?