http://www.cam.ac.uk/research/features/ ... of-change/
Languages become threatened for a variety of reasons – there might, for instance, be political, religious or cultural forces at play. “But for many endangered languages,” said Dr Jones, “the reason they are vanishing is because people don’t want to speak them any more. In a nutshell, they perceive the native language as outdated and the new language as the language of progress.”
A changing view of the world around them has, Dr Jones believes, had an impact on speakers’ motivations to speak Channel Island French. Events in the 20th century, such as the growth of tourism and the offshore finance industry, led to English being seen as a means to prosperity and social advancement, and also brought in their wake large-scale immigration to Jersey and Guernsey from the British mainland.
There's much more in the article than that, though, so well worth a read.
There are also short soundfiles.