My son doesn't seem interested in baby food.

My pediatrician recommended that we start our son on baby food at 4 and a half months, so we did. My son is now 6 and a half months, and he doesn't seem that interested in puréed baby food. I try to feed him about a third of a jar once daily and he doesn't even finish that little bit. Is anyone else having this issue? I know that breast milk (or formula) should still be his main source of nutrition, so I'm not too concerned yet, but I just want to know if other babies his age are more excited about eating!