SD cards make sense to me. Hard Drives... Now there is some spooky technology.

The reader head on a hard drive changes direction so fast, that it experiences accelerations like that of a bullet being fired, hundreds of times a second.

The "Fly height" or distance a reader floats above the platter is so tiny, that it would crash into a thumbprint.

The actual magnetic media that stores your data is a layer of iron a few atoms thick deposited on to a ceramic or glass platter, with a single atom layer of a protective metal coating (typically rhodium) in top of it.

Despite these incredible tolerances, they damn things are dirt cheap, and surprisingly reliable.