Why is it so hard to give a good elevator pitch?

I was watching a video of the company Smarketplaces pitch venture capitalist Mike Suster.  When they open with their elevator pitch, the first attempt was:

"We provide a market place service for bloggers.  We enable them to easily embed a content driven community marketplace into their site."

Then the second entrepreneur jumps in with:

"Embeddable Ebay or Etsy on their blog site."

Mike gives them the advice to only use the second pitch.

At Founder Institute we give first time entrepreneurs advice in Pitch Bootcamp to follow the format:

My company, ______, is developing (concrete product) to help (a target audience)  (solve a problem) (with secret sauce).

An example that fits their pitch into the forma would be:

Our company, Smarketplaces, is developing an embedable Ebay / Etsy for bloggers to monetize their traffic by making it easy to sell items related to their content.

Great video showing a professional investor giving honest feedback about what he is hearing.