They also want a definite exit strategy. Most look to going public in 4 to 5 years. There have been entrepreneurs who have become fabulously wealthy using VC's to finance their start-up. It can happen, several VC's say they are happy if one out of ten of their investments hits it big. VC's sometimes invest as financial buyers.
Public companies receive a premium price for the liquidity that the public market affords.
Going public is not without its downside. And, many offerings don't get completed. You commit yourself to operate in the public fishbowl. You put a whole extra layer of government red tape expense on your company once you are public. Some entrepreneurs can't or don't want to deal with such an environment.