neither is a person who writes and calculates things. I can do math in my head if I so choose. always have been able to, to include basic exponentials and log base of 10. some basic equations but I can make a mistake. one can argue that but well simply put, copy all completed homework and store the file where you know its archived. I have done this with a few online only things that I must have printed or photos, since well most cameras are digital and few buy film cameras. which is another subject.
I know that a machine does make mistakes but its also more likely the user who inputs the stuff is the root cause of the problem. I made a mistake on a read and the customer got the bill. the human back up to me didn't send us out to recheck the read and forced the read to be billed. 1700 dollar bill. it wasn't the machines fault but myself and the other in billing.
with writing things down. I do still see the need for that. at work I often will still as I must with check reads or as I often do. I read meters the day(work day) before, ie if I didn't have the new guy Monday. I would have wrote about 100 reads down and inputted them on Monday before I started.i do that to save money.
However, using your argument, cars can brake down, fuel lines can be backed up , ie been there with Irma. better have a horse, or bike just in case. see where I can go with this. and on paper work. with the army, any branch of government any and all important paperwork you must have, better copy and store as well that person can loose them too. I have copies of my retirement orders, both dd 214s. the ngb 22 which is the ONLY way I will collect my retirement is also stored both ways.
people loose their birth certificates , here these are archived and can be copied for a small fee.