I agree, it should be as simple as that. However, try to convince marketing folks that their custom built and very expensive product ads in the shape of a carefully crafted Flash animation have exactly the same effectiveness as a static image. Their careers are too invested to even stop and analysing what they are doing.
As (I believe it was) Henry Ford said, 90% of all advertising is useless. The problem is that there is no way to know which part of the whole is the useful 10%