I'm not entirely sure this is on-topic, but it definitely needs a programmer's understanding to be answered, and deals with general development (for a specific scenario) as opposed to a specific piece of code. In a way it also translates into "what are the challenges in doing X in a touch screen app", and similar questions have been asked here in the past. So here it is:

When Apple didn't implement copy-pasting on the iPhone since version 1 I just assumed it was a UI issue- they were waiting until they figured out a good UI for it. But now the idea is out there, and Microsoft still released Windows Phone 7 without copy-pasting, promising it'll be ready in a few months.

My question is: why does this takes a few months to implement? Are there some technological challenges that are unique to programming for a touch screen that I'm not familiar with?