Then when they meter gets changed to one of those new fangled smart meters, they'll put in a 100A main fuse.
Meter fitters do not have the authority to uprate a fuse.
There have been issues with 100A fuses in cutouts. The fuses will take a sustained overload for a considereable period of time and if subjected to such an overload the fuse carrier gets very warm, some of the fuse carriers in the newer cutouts were unable to cope with this heat and became damaged.