It used to work like that in an old version of Opera back in the day (perhaps Opera 5.0? I think it was the same version that introduced gestures),but a bunch of sites saw it as insecure and blocked Opera users from their sites so they backed down and switched to the standard method.

When you open a new tab, the original tab continues to run in the background, but you can't do that for your history.

Imagine a page which shows a number that increments every second the page is loaded. When you open a new tab, it continues to increment. When you go back, should it continue from where you left it, or behave as if it was loaded the whole time? The answer will be different for different sites, and the browser's default behaviour will sometimes be wrong.

This is how mothra on plan9 works. It's really an underrated browser, it has no tabs because it doesn't need them.