‘“Why not just have a higher setting cold and not have to retorque when warm?‘
Gaskets settle during/after first heating cycle. Cast iron heads are retorqued hot but aluminium heads must be left to cool completely before retorquing after the first running. Also it depends on the bolts and gasket material. Always follow the gasket supplier’s instructions. Original workshop manuals can become obsolete, for these instructions, when modern materials are used.
Many (most?) modern engines do not require retorquing - the bolts are torqued to the ‘yield point’, at fitting, and must not be tightened further. These engines do not use the old copper three layer gaskets, but special composite items. New bolts are required every time the head is replaced due to being stretched to the ‘yield point’.
Hope that helps. RAB