A tab bar is similar to a bookshelf for me: I see the icon and title of open websites in a neat list. Closing tabs and banishing them to some hidden history/bookmark menu is like putting your books into boxes in the basement instead of a shelf. Sure they're still there, but you might forget you have a book because you never see it and you have to dig through boxes to find it.
If a closed tab only remains in the bookmarks or history it might as well not exist for my brain.
> Closing tabs keeps my machine fast and memory usage low
I just restart the browser now and then, which will unload all tabs again. They're still in the tab bar but require almost no memory until I use them.