Native speakers learn the language at a time when they can't read or write, so they have to rely on their listening. Non-native speakers on the other hand usually first see the language written down, and then hear / pronounce it, and connect the writing with what they hear.

If I had a penny for every time a native speaker wrote "would of" instead of "would have" in forums, I'd be a billionaire. "Their" / "They're" / "There" is also common.

But the funny thing is, I noticed I would make similar errors after being immersed in a native environment after a few years time. Somehow I just say to myself what I wanted to write, and the slip-up happens. So native speakers are more prone to this, but it's not only there privilege!