Come now, that's being a bit hysterical/hyperbolic. There's plenty of other things you could do in the course of your command-line activities that are at least as destructive.
I know your example is meant to be trivial but there are plenty of ways when you're mucking about with pipes to ruin your day.
Like I say, "it is known" that git checkout is destructive, and while I can sympathise that perhaps the "-rf" is implicit I honestly can't see how you'd end up doing something like that in day-to-day activities, and if you did ... well if you'd spent any significant amount of time on it it probably should have been checked in anyway.
EDIT if you want to see some "good" examples of how you can inadvertently trash everything take a look at https://svnvsgit.com/ (warning, not as impartial as the title might suggest).
I'm not being hyperbolic or giving a trivial example (whatever that's supposed to mean), I was completely seriously pointing out that people used to apply your exact same victim-blaming logic to that same scenario until others finally made them come to their senses and realize that, just because the user happens to type in a command that tells the computer to shoot him in the face, that doesn't necessarily mean the computer should actually go ahead and shoot him in the face. Somehow you managed to take those 6 words out of context and focus on bashing the example while ignoring the actual real problem I was illustrating with it in your reasoning.
A "trivial example" is where you demonstrate a concept using a simplified or trivial scenario. It's quite a common term, and I didn't mean it as a put-down.
"victime-blaming", "shoot in the face" .. I feel are fairly extreme terms to describe what's happening here. The scenario you've concocted is really only one that could occur where you didn't know what you were doing and Git (or the command line) aren't really things you'd end up using if you didn't know what you're doing.
It's not a concocted scenario, the cli command in question explicitly has a property that defaults to preventing it from doing what it should do, unless you override the property. Explicitly because it's so destructive when you do it by mistake.
Come now, that's being a bit hysterical/hyperbolic. There's plenty of other things you could do in the course of your command-line activities that are at least as destructive.
I know your example is meant to be trivial but there are plenty of ways when you're mucking about with pipes to ruin your day.
Like I say, "it is known" that git checkout is destructive, and while I can sympathise that perhaps the "-rf" is implicit I honestly can't see how you'd end up doing something like that in day-to-day activities, and if you did ... well if you'd spent any significant amount of time on it it probably should have been checked in anyway.
EDIT if you want to see some "good" examples of how you can inadvertently trash everything take a look at https://svnvsgit.com/ (warning, not as impartial as the title might suggest).