Why or why not?
range() returns a list, xrange() returns an xrange object.
xrange() is a bit faster, and a bit more memory efficient. But the gain is not very large.
The extra memory used by a list is of course not just wasted, lists have more functionality (slice, repeat, insert, ...). Exact differences can be found in the documentation. There is no bonehard rule, use what is needed.
Python 3.0 is still in development, but IIRC range() will very similar to xrange() of 2.X and list(range()) can be used to generate lists.