[Gracana]

The point is to say it's an error in an automated system, rather than a human who decided to intentionally send out notices to 120-year-olds. Of course humans programmed the system, but they surely didn't mean to program it to do that.

[burkaman]

And more importantly, the humans who programmed it probably don't work for the selective service. Obviously all "computer errors" are technically the fault of a human somewhere down the line, but in common usage it means that "I didn't make a mistake, the computer didn't do what I told it to do".