I saw them at the store and said hi but they were busy
Is there a reason that you wanted to say hi to them?
I want to say Hi because I wanted to spend time with them
Just because they were busy doesn't mean you should feel hurt by it. Everyone has things going on in their life that you might not know about so don't take it personally if someone can't spend time with you.
Why the fuck do you care so much? I mean if they wanted to spend time with me, I would have made time for them.
I am glad that you are able to make time for people but you cannot expect them to always do the same. Not everybody is able to deal with time the same way, maybe they get easily overwhelmed and cannot manage their time well.