Big players in the stock market, hedge funds, banks etc have the ability to hedge and leverage risk with different processes such as short selling and many other tactics.
A VC will think like an investment bank but have limited potential to save themselves in a moment of bad judegement.
School yard mentality too, once its clear everyone is getting involved, due diligence shows that there is some sort of hype building then they follow - it takes a lot to be the first especially in a playground of Silicon Valley and startups.
(I have never dealt with any form of VC therefore this is my judgement and idea going from the mass amount of reading I've done)
Even discovering an investment opportunity doesn't come equally easily to all firms. As in any industry, there are those who find/do things for the first time, and those who hear about the first group and jump in.
Finally, the competency disparity between leaders and followers isn't as big as it seems. Many of the leading firms won a lucky bet and now make money simply by attaching their name to a project. Or, they are connected and can create income and offers for their investments while the follower firms don't have those advantages.
There are dozens of factors that go into a VCs decision, everything ranging from the age of their active fund to how well the relevant partner gets on with the founders.
Not every deal is right for every VC.
Also you need to be careful of survivor bias, for every Groupon that succeeds there might have been a hundred that looked identical to it at seed-stage but ultimately failed.
I think some do, but remembering this 3min talk by Derek Sivers http://www.ted.com/talks/derek_sivers_how_to_start_a_movemen... about leaders and followers, we need more followers than leaders. Once a lead investor is established, bring on the followers, startups need traction with investors too of which not everyone can be there first.
The question becomes which investors are known leaders and which ones are followers.
Feel free to chime on Quora too: https://www.quora.com/Venture-Capital/Companies-are-unfundab...