Why must cranes be assembled on-site?

Cranes are often assembled on-site primarily because they are too heavy to transport intact. The size and weight of cranes, especially larger models, make it impractical to transport them as fully constructed units. Disassembling and transporting individual components is necessary to meet transportation limits and ensure safety. Once on-site, these components can be assembled into a usable crane structure suited for the specific lifting tasks and conditions of the job site.

The other options suggest reasons that do not accurately address the logistical and physical limitations associated with transporting cranes. Ongoing maintenance is important, but it does not affect the requirement for on-site assembly. Difficulty in operation relates to operator training and skill, not assembly logistics. While specialized tools may be needed for assembly, they are not the primary reason for the on-site construction of cranes. The challenge lies predominantly in their size and weight, making on-site assembly the most efficient and practical approach.