I would guess you had them for sale for the last 6 months at a price point higher than $7.50 Ea. Did you lower the price at the same time as posting them here? I would guess the price point sold them fast. Either way, it isn't unreasonable to expect positive feedback from buyers if they were happy. However, I know, I rarely have left feedback to sellers on Amazon. Not that I don't want to, for some reason I rarely even look at feedback on Amazon when making a purchase. I have always looked at it in a different way than Ebay when buying/selling.
If you are/were just looking for positive feedback from the sale(s) I guess it would be a dissapointment.