I stash for many reasons, one is when inspiration strikes , I can act on it without having to go to the store. I find it distracting sometimes to have to go and search out ... I am much more likely to finish a project if I can start when I really want .
I stash because over the years often when I see a fabulous fabric ... it will probably be gone when I finally figure out what I will do with it. So for me the process is different its fabric first .. Figuring out the project for the fabric is second.
Additionally I do not want to always pay full price .. so when I see a piece I know will have use on sale I buy it.