He was bred for war from birth so he'd never have had a chance and if the chance did come up, he wouldn't see the opportunity due to his conditioning and training.
Not sure if you're kidding or not but just in case you're not.....excuses how?
Again, I'll bring up that awesome movie Soldier since Halo seems to resemble it so much in part but Kurt Russell had issues with connecting to others, always addressing the civilians he was forced to live with as "sir" or "ma'am" and patrolling and guarding due to him being trained from birth to be the perfect soldier and not knowing anything other than war and training.
I imagine John will be the same in the Halo series and the only interactions he's had that didn't involve giving or receiving orders were with Cortana.
Getting awfully tired of GameFAQs mods removing my posts for being "offensive" when I've done nothing wrong