"The button does say backSPACE on it. And NOT backPAGE."
How many keyboard keys get different "meaning" in different applications? If you're in a text-editing field, backspace will delete the previous character. If you're outside it, it will go back one page. I think Mosaic did it too - I never used Tim's first browser, but maybe it did it too. What should they have used? Maybe an eMacs combination like Ctrl+AltGr+LeftShitt+CursorLeft+B? Or a vi command like :b1wp
Think, pressing the spacebar will also scroll the page. Usually that large button says nothing, so maybe it's right? Yet BACKSPACE means to go back one space, not to delete the character. Because in typewriters, when it appeared first, it did exactly that. So it's time to rename it?
Anyway my keyboard has only a long left pointing arrow. Many non-English keyboard have only a symbol. Also, when first browser appeared, not every system had the keyboards with all the keys PC users are used to.
Full keyboard support is very useful when you don't have a mouse (in some server rooms, it happens...), or you have a real bad mouse support in some remote consoles.