Normally I don't get annoyed by things like this, but the last several times
I've taken my time to send out seeds and/or plants to people I've received not
one word. I wonder, did they get the plants/seeds, did I waste my time? My
money?

I've had the same experience in a number of situations, including "desperate"
people featured in reputable newspapers who have a very sick child, etc. I've
lost count of the times I sent off a small or not so small amount to the
address cited. So far, I have gotten back a total of one thank-you note.

I don't have a clue as to this behavior among your recipients or mine, except
perhaps they were brought up to feel "entitled" to anything they could wheedle
out of another person, and not obligated to thank a sucker.

Maybe, too, the rather ungeneous thought arises, they live in a subculture
where a sick child is not automatically taken to a doctor, you ignore your
landlord until a notice to vacate goes up on your door, etc.
zemedelec