You might not think that it's that hard to be random, but creating truly random numbers is quite difficult... and these digits underlie and protect almost every digital transaction we make. Most normal computers "are completely deterministic and are therefore not capable of creating truly random numbers," as Physics World reports. They are, in other words, designed to do things repetitively, the antithesis of randomness. Cryptography systems generally rely on "pseudo random-number" generators, which are close to random but not completely, making them possible to crack. One recently revealed NSA backdoor involved a clandestine pattern "baked into" a Federally approved number generator, which effectively broke it.
One way to create random numbers is to measure random phenomena like the noise in an electronic circuit, but such processes are often unreasonably slow or expensive.