What is a reason for not undercutting the sides of an excavation?

Not undercutting the sides of an excavation is crucial primarily because it can lead to cave-ins. When the sides of an excavation are undercut, the structural integrity of the soil is compromised. This destabilization increases the risk of the surrounding soil collapsing inward, which poses serious safety hazards to workers inside or near the excavation site. Cave-ins can result in injury or fatalities, making the adherence to proper excavation safety protocols essential.

The other choices do not align with the main reasons for avoiding undercutting. Improving visibility may seem beneficial, but it does not outweigh the safety risks associated with cave-ins. Similarly, while digging might be easier with undercutting initially, the long-term safety implications far overshadow this advantage. Cost factors also come into play, but they should not supersede the primary concern of maintaining a safe working environment.