I haven't seen it on any other car, but one van I had a few years ago had a cutoff switch under the hood
that was a marine switch(will outlast the van! heavy duty switch made for rough weather/locations) , normally used on boats. (A mechanic acquaintance told me, and he had seen them used before also).
It might have been used because of cold or unknown battery drain,
OR it might have been a theft deterrent, I don't know which.