Why is plan bracing needed in a mobile scaffold?

Plan bracing is essential in a mobile scaffold primarily to prevent the scaffold from twisting when it is being moved. This method of bracing adds stability and rigidity to the structure, ensuring that it maintains its shape and vertical alignment during transportation. Without adequate plan bracing, the risk of the scaffold twisting increases significantly, which could lead to dangerous situations such as instability or collapse while in use.

The other options do not address the primary concern of structural integrity and safety associated with mobile scaffolds. Enhancing appearance, increasing working space, and boosting load capacity are all important considerations in scaffolding but do not specifically relate to the inherent need for stability while moving the scaffold. Thus, the focus on preventing twisting directly correlates with ensuring safe and effective use of mobile scaffolding.