I think it's easier to appreciate the skill involved in making a piece of art than it is to appreciate the art piece itself. Some people (myself included), may even prefer appreciating the skill in and of itself, independent of the art.

Further, I think it's easier to comprehend how difficult it must be to produce a realistic sculpture or painting or what have you, compared to an abstract piece. As the piece becomes more abstract, appreciating it requires, I think, a lot more contextual information that the viewer may simply not have.

Of course, some art may just be crap. Who's to say?