It should be viewed in an evolutionary perspective. If you had an equally functional amazon website that used only basic HTML elements, which is orders of magnitude lighter (but still loads in about the same time for most users), which one do you think would succeed?
Do (most) users need all the shininess? Nope. Do they (most) prefer it? Absolutely.
Each product has an optimal "clutter" (in competitive terms, maybe a "Nash equilibrium"?) -- a good example is the Google homepage/search results; anything more complicated is clearly unfavorable in terms of competition, unless you offer a qualitative improvement.
Do (most) users need all the shininess? Nope. Do they (most) prefer it? Absolutely.
Each product has an optimal "clutter" (in competitive terms, maybe a "Nash equilibrium"?) -- a good example is the Google homepage/search results; anything more complicated is clearly unfavorable in terms of competition, unless you offer a qualitative improvement.