Memories in the brain are spread over an ensemble of neurons. Like actors in a play, or musicians in an orchestra, each neuron contributes to the whole memory but isn’t essential – you can lose one or two and the memory will be degraded, rather than suddenly wiped out.
On the other hand, if you damage a few sectors on your hard disk, the 1s and 0s in that portion of the magnetic platter are useless, taking down all and only their data. In other words, the representations on a hard disk do not fade or degrade or weaken. They’re either there or not.
However, the brain’s amazing robustness to change and injury comes at a cost. A hard disk may be brittle (like glass), but if it’s undamaged, its storage is perfect. On the other hand, a brain won’t ever shatter, but it’s easily deformed (a bit like silly putty).
These are storage systems designed with different tradeoffs in mind: on the one hand, brains still work in the mud and the rain; but, they aren’t so good for storing bank transactions…