Because the typical standard of consent is that in order to do something to someone, you should have informed consent. If you cannot obtain that, then you do not do the thing. Something that does not exist cannot give informed consent, therefore you should not do the thing.
Because the typical standard of consent is that in order to do something to someone, you should have informed consent. If you cannot obtain that, then you do not do the thing. Something that does not exist cannot give informed consent, therefore you should not do the thing.