We are constantly losing technology as the treadmill of technological progress continues. Casette tapes, CRT displays, and perhaps photographic film are some examples. One can argue that there are "strictly better" technologies available now, but there are always niche cases where the new and obsolete technology are not quite fungible. What if for some reason a modern industry gets wiped out? Then we'd have to revisit the lost art.

As an immediate example, my wife's business needs p-channel small signal JFETs. These apparently are no longer fabricated, and with the way the semiconductor industry moves, they are likely never coming back in any appreciable quantity. So once the world's supply of obsoleted semiconductors dries up, the technology will basically be lost.