You are not alone in your shopping habits.
I always consider the container when buying food. Always buy plain yogurt in the big tubs - when they are clean I drill holes and use these to give away plants at our local swap.
Buying Luigi's Lemon Ice gives me small, flexible plastic cups which are idea when cleaning and packing seeds. The plastic flexes enough that I can pour the cleaned seeds into the small plastic bags without spilling any - no funnel needed. Oh, and I discovered that the clear plastic lid from Pringles fits snugly on the Luigi's container which is perfect for larger quantities of seed.
(I'll go back to lurking now...)