Why not a photo programme that does what the consumer wants?
You're not the only consumer and what you want is not necessarily what other consumers want. So there are two photo apps on your Mac. One for the folks who like non-destructive editing called Photos and one for folks like you who prefer to trash their original files. That's called Preview. There are advantages to both systems but you'll find most photographers prefer non-destructive. It means there's opportunities to fix mistakes :)
My motive is Memory management
I suspect you mean disk space management. For the ones who prefer non-destructive editing then there is the fact that disk space is inexpensive and running a Photos library from an external disk is simple.
In any event, the moral of the story is to use the right tool for the job :)