The government also stands to benefit greatly if they throw their weight behind smart ideas, just like VCs. It would be interesting if the government could fund itself with investment.
The US government invests in growing the economy, or tries to, which increase tax revenue which gives the government more money.
edit: Also it's not that top VCs are better at finding investment but rather that their social capital means they provide values to companies beyond the investment money. As a result companies that are doing well which choose to take money from top VCs versus other VCs. As a result the model doesn't scale since there's a limited pool of top companies to invest in.