The difference here is that tabs capture intention whereas history captures everything. A page remains in a tab because you opened it and didn't choose to close it; that's a signal. Example - if you are trying to find something elusive, you might end up opening a dozen blogspam pages in tabs and then closing them immediately because once you see them they're obviously useless. They are now gone from the tabs. By contrast the history will remember them forever and show you them, even though you don't care.

I use them as favourites rather than nostalgia, so even I think this use case is kinda crazy, but I get it. Tabs work really nicely without deliberate thought, you don't have to choose to save things, you don't have to choose to dismiss things, stuff you were at least vaguely interested in just sort of accumulates effortlessly as you use the browser in a natural way. There may be something browsers could offer to do this better, but it would be a hard problem.