The leader rules were designed a long time ago to lessen the amount of crack offs when the more powerful casts are being used .

The likes of a otg or pendulum cast has the lead traveling around the caster rather then a arc over the top so there is a danger that the lead could head off down the beach .
It was carried over into the casting world for the same reasons and also after a cast or two the leader knot may have been slammed into the ground possibly weakening it so theres a good safety margin built in.

I use 70 to 80 lb on the field and 40 to 50lb on the fishing gear .

A freespool caster will also get greater distance from using .25 line as there will be less x wind drag and the weight of the trailing line is also lesser .