Externally, the XB-70 looks like a bare-bones design that stresses simplicity and function over aesthetics and flair. It doesn't bother with looking cool. It doesn't have to bother with looks at all. Mach 3 has a coolness all its own.
Ah no, my dear Murdoc. The XB-70 looks very cool indeed, just as it is. That she hustles along at Mach 3 is icing on the cake.