When Apple took on touch, it created a new OS (though, yes, based on OS X) with entirely new UI conventions. It threw out everything end users knew about getting around in software and started building anew with the finger as the foundation. When Microsoft took on touch, it first tried to bolt it onto Windows 7, then got off its ass and built an entirely new interface for Windows 8. This time Microsoft used the finger, but also the pen, as the foundation.
When Google took on touch, it slapped a web browser in a traditional PC notebook, gave it a price tag of $1,300, and said 'good luck tapping tiny 30-year-old UI buttons designed for mice and keyboard shortcuts'.