Sounds like a common thing but I've seen people that get a new plant and never give away cuttings or share seeds. And I've never understood why they do this. Mainly its members of garden clubs and there is a bit of competition between people. Now that we have online shops the idea of places never seeing new plants is hopefully a thing of the past. I'm part of the group that shares even if they don't want it.
I even order extra plants to give to other gardeners. The idea being if I kill mine there is a spare to get a cutting from. And my seed collection is allways open for mates to grab something new to try. I planted some gourds but due to lack of watering on my part they didn't make it. They only came in packs of 10 ish seeds and I had allready given some away. But they had a bumper crop and dropped me in 5 dried gourds full of seeds as they had 50+ and were still working out what to do with them. So moral of the story is I've got a swag of seeds to have another go at growing. And so far a new scoop for the chook feed. Sharing plants and seeds is an important part of gardening and sometimes you can be surprised by the plants you get in return. I'm planting elephant garlic that a mate gave me that I couldn't get online and had no idea he even grew. 
