Apple is a very large company which means that everybody has heard of it. They get press coverage galore from blogs all the way up to national television. The average Joe knows what an iPad is. It makes an explanation much less painful if you can compare it to something familiar. The average consumer doesn't really know an iPad from an HP Touchsmart so anything helps.
Being the giant that it is, Apple is also the company to beat. I can't count the number of times I've seen the phrase "iPhone/iPad killer". You could sell one million toothpicks for five dollars a pop if Steve Jobs endorsed it. Android just started to overtake Apple in the smartphone area. The next step is the tablet area. Apple creates a niche, and then everybody else wants a piece of the cake. That's what's happening with tablet market right now.
I don't have a problem with Apple, but I do get very sick of everything getting the fruit comparison treatment. I will continue to do as will the rest of the world. They are the third largest computer manufacturer for a reason.