The simple answer is that acquiring large tracts of land isn't tractable in established areas. It requires forceful taking of some parcels or extravagant expen

The simple answer is that acquiring large tracts of land isn't tractable in established areas. It requires forceful taking of some parcels or extravagant expense. Eminent domain allows the government to accomplish infrastructure projects at a (somewhat) reasonable cost but there's no expectation that private entities can achieve the same thing.