Well, there's Junk DNA - generally non-coding DNA, some of which does have some "purpose", arguably - and then there's Junk DNA.
Having a broken gene for vitamin C production makes no sense any way you slice it - except evolutionarily.
29+ Evidences for Macroevolution: Part 2
Having retrovirus segments in common with close evolutionary relatives in the same location, ditto.
29+ Evidences for Macroevolution: Part 4