This happens because English as Second Language teachers are often non-native speakers and speak with an accent themselves. They are able to teach grammar or vocabulary but they cannot teach pronunciation. Often non-native speakers are only exposed to a native speaking environment as grown-ups. By that time your brain is already stuck in its ways and it is frustratingly tough to learn new vowels and consonants.

As a non-native speaker myself I can often hear myself pronouncing English poorly yet I find it excruciatingly difficult to pronounce some vowels the way I intend to pronounce them, even though I have been living in a native-speaking environment for a long time. Similarly, my native English-speaking (American) wife finds it very difficult to pronounce some vowels and consonants of my own native language. It took her fairly long to learn how to pronounce my name correctly. (Ironically, now that we're married it is her name as well.)

All I am saying is that I would not attribute this to pride or laziness. Pronunciation is a genuinely difficult thing to learn as an adult.

Thanks for that perspective. I certainly didn't mean that all ESL speakers exhibit wanton mispronunciation. Perhaps none do. In fact, your eloquent rebuttal has left me sympathizing with even Arnold Schwarzenegger.

You can learn syntax and vocabulary quite easily by reading and writting in a language. Pronunciation is much harder to learn, often requiring relocating yourself.