(For some reason the iPhone YouTube app's icon was an image of a retro cream-and-brown 1940s TV. I guess Steve Jobs just liked that design because it certainly didn't have anything to do with YouTube's branding and didn't look like anything Google would have picked for any product.)
When Microsoft shipped the revamped Windows Phone a few years later, the "app gap" was one of the main problems. High-profile apps like YouTube never became available on the platform because by then Google was busy promoting their own mobile OS.