Except, that sort of thing is important in places like gevent, pytest, and numba, and that functionality isn't easy to replace without a lot of additional langu

Except, that sort of thing is important in places like gevent, pytest, and numba, and that functionality isn't easy to replace without a lot of additional language/stdlib work (no sane developer would reach for it if other APIs sufficed). The absurd example of overwriting the literal `10` is "obviously" bad, but your assertion that the interpreter should be able to assume nobody is overwriting its memory isn't borne out in practice.