Rational only means strictly profit maximizing under simple economic treatments. In this case, we're talking about improvements that boost land value, but must

Rational only means strictly profit maximizing under simple economic treatments. In this case, we're talking about improvements that boost land value, but must be agreed to / enforced on all. Consequently, you deal with local optima, when everyone is perfectly individually greedy, no improvements can be constructed, and everything is less "good" than it could be (for the individuals and society).