Shortage of lenses?
I also have 16mm f2.8 to 300mm f2.8 covered in prime lenses. Infact a number of them are at focal lengths that aren't available from other manufacturers.
Also keep in mind that Pentax has a long history of backwards lens compatibility and there are over 200 different Pentax lenses, (plus third part offerings), that are useable on the Pentax K20D. Furthermore they all work with focus confirmation and image stabilization.