I have read several articles on feature detection and that it is more reliable than browser detection because browsers lie.
I couldn't find any information on why they lie. Does anyone know the reason why they would do that?
As far as I understand it, Webmasters do browser sniffing to find the capabilities of a browser and limit what they send to the browser. If a browser lies about it's capabilities they will receive more from the webmaster, you can read more: