Working within the 'inner cities' back many years, the 30 amp plug fuses were what I found in the majority of the fuse panels. HOs and tenants bought them 'cause they lasted longer' that the 15-20 amp ones. They had no clue, except the economics of buying the 'longer lasting ones'.
I also came upon many instances of 'warm' fuse boxes, and toaster wire!
The S adaptors that I installed were bastardized and higher amperage S fuses were forced in.
Over the years, I also came accross copper pipe used for 30, 60 & 100 amp fuses in disconnects!
Fuses are not to blame!
