Not to defend stupid movies, but Kyle Reese explained to Sarah Conner that most of the digital records got wiped out when SkyNet nuked all of humanity, so they only knew John Conner had a mother named Sarah who lived somewhere in the Los Angeles basin.
They only way they could guarantee John Conner would never be born is to kill her and document her death completely.
The first T-800 they sent altered the time line enough for Sarah Conner to get pregnant—not dead—by Kyle Reese himself and therefore John Conner was really John Reese.
So if humans fight back, did skynet run out of nukes? (I’ve only watched clips, since I’m not much interested in watching sci-fi movies.)