> If people in a community pooled their own money together to build a new bridge then you'd have economic activity that is created due to real demand and there would be a real incentive to make sure they are not overpaying or that their money is wasted.

Isn't people in a community pooling their money together what a government is? Often the increase in property values alone is more than the cost of building the bridge, the difficulty is co-ordinating them.