I often use scanner / printers as an example. Its like a robot with a very specific and easy job - feed the paper through one sheet at a time. They've been around for 40 years, mass produced, they still cant reliably do that one thing.

With a lot of tech, it seems like solving the first 90% of a problem is easy, then the next 5% very hard and expensive, but the last few percent is impossible.

We see this with so many things - printers, roombas, self driving cars.