The key distinction here is that native English speakers speak with whatever dialect that they grow up with. On the other hand, most ESL speakers try to learn a so-called "Prestige" dialect, like RP or General American. Thus, most fluent native speakers have a more prestigious accent and way of writing due to this, than those who speak English as a first language.
That's a great point that I haven't thought of before! I tend to forget that when others learn a new language it is generally taught in the proper and/or polite manner.
