For one, you're pretty much guaranteed its going to grow in your garden.
When plants are grown, and the strongest selected for seed saving, you've taken the very best nature has to offer to captured it for the next generation.
That seed gene has already proven itself, so its just a matter of taking that and replicating it generation after generation.
A local seed saving group is one of the best ways to do this. You'll be surprised to find there are plenty of expert seed savers out there, just looking to swap seeds and share their knowledge.
Seed needs to be kept growing and circulating through the system. It doesn't pay to store it away 'just in case' its much better to have those plants growing, setting seed, adapting to climatic changes along the way, then that seed being collected and the cycle kept going.
By setting up local seed swap networks and plant swap networks too, you're taking a big step in the right direction to ensure food security and food sovereignty in the future.