What answer do you want? Photos doesn't do the thing you want it to do. Yeah it would be cool if it did, but it doesn't. People were just trying to help by offering suggestions on how to do the thing you wanted.
Of course, you did not ask people for help with doing the thing, you just asked "why" Photos can't do the thing and also "what's the deal". The "why" is that Apple hasn't added that feature to the Photos app. Why they didn't add it, WE do not know for sure. You'll have to ask them. I don't think anyone here can provide an answer that would satisfy you.
"What's the deal?" might be that Apple only wants to provide basic functionality for their built in apps and leave the rest to 3rd party app developers.
Now, if you just want to complain, that's fine, but then don't ask questions if no possible answer would satisfy you. Just say you're not happy about it and let us all move on.