Why do the Irish believe in leprechauns?

The Irish do not believe in leprechauns. As a born and bred, true Dublin man, I can honestly say I've never met a person that 'believed' in them. In fact, I've never had a conversation about them. The myth probably goes back to the old stories of gold under the rainbow, and that would be where you'd see a leprechaun. And this might symbolize our inherent positivity, despite our small physiques and red-hair; and those of us who are from the country would have a fiddley-dee accent, whereas the majority of Dubliners have a Colin Farrellesque accent.