I had to learn himem.sys and loadhigh when I was about 10 years old and the family PC HDD crashed. I had a copy of DOS and a manual the size of a phone book. The only way out was to write my own boot disk.
But yes, these days it's a bit of a useless skill.
I the sort of person who would go to the dealership and start looking underneath the showroom cars. If I can't see the oil filter, I don't want it.