I've had this discussion a number of times with my non-photgraphically inclinded friends. Even they are noticing this trend. It's the visual equivalent of the Loudness Wars in music.
Basically, the louder something is (loud in this case might better be described as "sensory dense", instead of just high volume), the more it grabs and keeps attention. Listen to any Top 40 song today and you'll hear layers and layers of sound, you'll also hear compression (which is not file compression, but the audio equivalent of HDR). What they found in the 80s when CDs allowed an audio dynamic range much larger than vinyl was that wide dynamic range music grabbed people's attention and made them less likely to change the radio station. It is the same as high fat high sugar food - it may not actually taste great, but it grabs us and addicts us.
First there was dodging and burning, then highly saturated colors (ever notice that Kodak consumer films are higher contrast and saturation than their pro C41 films?), eventually he had HDR (which is just an extension of or replacement for dodging and burning), then came heavy handed use of complimentary colours (the so called "cinematic colors"; everything being blue and orange), and now we are back to lots of lens flares (those really seem to come and go in popularity every couple of years). In the end, you stack it all together and you get this massively garish sensroy dense image that grabs people by the eyeballs and shakes them. I'm sure some people use these techniques because it is what they are used to and think they are supposed to, but the advertising agencies are using it knowning full well how and why it works.
For all the hatred against the hipsters and their lo-fi low-contrast, flare prone, lomo images, I much prefer those "simple" dreamy photos to what I'm seeing commercially.
