Apple simply does not engage in anything even remotely resembling astroturfing. The simplest reason is that they don't need to, but the more accurate reason is that it's not in the company culture to do things like that.

As a semi-related example, I'm sure you're familiar with product placement in TV shows and movies. Most product placement is done because the company paid for it to be there (for example, all of the Windows 8 stuff I've seen in Arrow I'm certain is paid product placement). However, despite the fact that Apple products are used frequently in TV shows and movies, Apple does not pay for product placement; all the Apple product placement you see was free.

In any case, I personally don't think Apple is the only company that doesn't engage in astroturfing. I'm sure there are many large companies out there that don't do it.