The primary reasons for not burying all power lines are cost and technical limitations. The high initial investment for undergrounding projects is often prohibitive, especially for long-distance, high-voltage transmission lines. Furthermore, overhead lines have a greater capacity for heat dissipation, allowing them to carry higher voltages and currents more efficiently over long distances. While underground lines are ideal for densely populated urban areas where space is limited and aesthetics are important, overhead lines remain the most practical and cost-effective solution for large-scale power transmission.