There are many algorithms where instead of transferring data using a computationally expensive (usually public key, like RSA) algorithm, the data is encrypted with a much faster (usually symmetrical, like AES) algorithm using a random key and then the key is transferred using the expensive algorithm.

If you can guess how the random key is generated, then you can decrypt the message without breaking either encryption algorithm. That's why it is important to have really unpredictable random data, and physical randomness is the best for that.

In practice, that wall of pendulums is unlikely to make a difference compared to the more mundane techniques used in most computers these days, that rely on some CSPRNG combined with various hard to predict system events (ex: interrupt timing), but it looks way cooler.