You should understand that VCs do not invest their own money but rather invest the money of "general partners" -- universities, pension funds, wealthy families, etc. Those investors are sophisticated and have very large portfolios relative to the amount of money they have allocated to VC (as an asset class). To gain access to their money, the VC had to both put on a song-and-dance about how they were going to get returns which were uncorrelated with the larger market (and huge) and then execute a series of contracts which constrains the VC's ability to do anything outside of the investment strategy which they've agreed upon.

It's not just a matter of "swinging for the fences makes me feel more fulfilled." It is "I have promised Yale that I will swing for the fences or I'll receive a call from their attorney asking politely for their $20 million back, and that call will be polite exactly once."