also (this is just me) I tend to want to give seeds to towns that seem like they are struggling, ie lower level people, people who are making spade progress but who seem like they'll miss the goals (I tend to focus on giving to people who give to me but then I branch out)
does a person who has 6000spades really need the seeds over someone who's at 1000 spades?
again, if they weren't a brand new (added in the past three days) neighbor I'd probably let it pass...it's also possible they think I'm more premium then I am (I have Frink, the pet store, Itchy and Scratchy studios and the cracker factory all near Monsarno because it's my commercial- factory district, I do buy buildings/characters but don't buy things like seeds.