Except when you're not sure what the word is pronounced like. The more obscure word, the easier just to switch to the native pronounciation and hope that it's m

Except when you're not sure what the word is pronounced like. The more obscure word, the easier just to switch to the native pronounciation and hope that it's more comprehensible to the audience than the inevitably botched "correct" version. This may apply to English more than other languages - in some languages it's pretty easy to guess how to pronounce complicated words after seeing them in writing.