Lots of gee-whiz fighter stuff here but the question remains as there is a whole world of super-critical swept wing aircraft in the business aircraft world. More than one of those has landed gear up and the results vary mostly dependant upon the terrain.
As for the fighter world I believe that the main cause for ejection would stem from the structure of the aircraft being more inclined to disintegrate on impact due to the higher wing loading/approach speeds when engine out. The standard response in most air forces is, if it stops pushing, aim it somewhere safe (time permitting) and get out thus hopefully collecting your silkworm pin.