I think these promises tend not to be fulfilled because of SCARCITY.
More and better healthcare, a better environment, minor reductions in defense, better education, better roads, bridges, sewer system, and water systems. All these needs to be fulfilled using vast resources - financial and human resources.
However, the government financial capacity is limited since it can't produce money at will without jeopardizing the economy as a whole.
Scarcity is an economic concept wherein the world has a limited means to satisfy unlimited needs. Thus, choices must be made. Promises will be fulfilled at the cost of the fulfillment of other promises.
