@Oneeyeking
>Our civilization has an amnesia
It's not that civilisation has amnesia, it's just that such knowledge has be passed through time over different methods, as for why this exact method was lost it's simply because it's very very old and due to historical event.

In the current "modern" time a similar example would be for example the Saturn V rocket.
A lot of the engineering methods used at the time are completely forgotten, because it was not documented and because other methods are used today.

Some other modern knowledge is simply lost because of copyright/patents/trade_secrets and many other bullshit.