Starscream kept you in his cockpit as he did some errands around Scorpinok base. Was he allowed to have a human? Undetermined. Thundercracker had a dog and G.I might as well have been Skywarp’s pet humans, why couldn't Starscream have one?

He kept you around because of your ‘Oh-so-eager-to-please’ nature and habit of stroking his ego. You complimented him fervently and it made him preen. Obviously he had to keep you around.

Often he would slink back to his chambers after getting his afterburner kicked into next week by Megatron. Pulling you out of the many compartments he kept you in and let you do the rest.

Somehow that's the only way you found yourself easily surviving in a world where your car could be an alien and you had to worry about jets in the sky wanting to end Earth. Kissing ass and being an overall suck up. Starscream ate it up anyway.