You might be dismissing the point too soon. To the lay-person, junk DNA looks like as useless a feature as a ridge in a door panel, or dummy pathways on a chip. To an expert auto-maker, the purpose of the panel ridges is obvious, structural rigidity. To an expert chip-maker, the purpose of dummy pathway is obvious. To Our Holy Creator Who Art in Heaven (or whomever you wish to credit our creation), it is possible that our junk DNA has a very obvious purpose that we have yet to divine.
Junk DNA does (or did, in many cases) have a purpose. Its just that any DNA which we don't understand the purpose for is labeled as junk. That definitely doesn't mean it doesn't do anything or that its useless.
