Low-stakes conspiracy theory: they were invented by word processing marketers to justify spell-check features that weren’t necessary.
Evidence: the Oxford English Dictionary (Oxford being in Britain) entry for “-ise” suffix’s first sense is “A frequent spelling of -ize suffix, suffix forming verbs, which see.” So in a British dictionary, -ize is preferred. But in a computer, I have to change my whole hecking country to be able to write that!
