Airliner incident blamed on settings punched into laptop - you mean it's manual? #airlines

Hmmm. Got the weight wrong by 100 tonnes. That's a large error. Trying to save fuel they set thrust at just enough for ambient conditions and runway length... or so they thought. I can understand how this happened.. it's easy enough to do some calculations and punch the worgn, umm, wrong keys in the wrong order... but why don't sophisticated airliners actually weigh themselves? They could (easily, I would have thought, with some sensors in the hydraulics) measure weight and the balance of that weight fore and aft on the undercarriage, before committing to a thrust value. In fact I thought they did do that?

The wrong calculation was made when pre-take-off calculations were made prior to departure, the Australian Transport Safety Bureau reported. It was found that the calculations were based on a take-off weight that was 100 tonnes below the actual take-off weight of the aircraft. The result was a thrust setting and take-off reference speeds that were lower than those required for the aircraft's actual weight.

There have been many, many incidents like this where the results were more drastic, including navigational blunders blamed on similar human error. So why isn't it automated, with a human over-ride?