I think Jack merely represents the average steerage class male at the time. (Who got lucky with a 1st class girl on the unlucky Titanic). It's an inspiring story of hope: That no matter how poor some blokes are, chicks dig spitting of the deck of a ship... and therefor might sleep with you in the back seat of someone else's posh car and steal your seat on a lifeboat. But hey that's only fare in 1912.