It's a rather unique charm and adds to the 'high action low dialogue' stuff. Since when people are talking they tend to call them by their name, refer to their name and such.
JOHN. Hey JOHN. Over here, JOHN. Etc.
I don't think they'll ever refer to his name but even if they do, it wouldn't really have much of an impact. Maybe it'll get revealed at the last part and Jack will point out how he used the name 'Jack' as simply a cover for his true identity. Plus, in the old times people believed you can be cursed using your own name, so there's also that.