Fun fact, being in pronation for long periods of time can put pressure on forearm muscles and restrict blood flow, causing RSIs. It's why a lot of ergo keyboards are tilted upwards towards the middle.
On the other hand (hah), pronation is super useful for throwing athletes - especially pitchers. Pronating during a pitch gives the ball a spin, which makes it fly faster. But it also reduces pressure on the shoulder by using the forearm muscles as a natural shock absorber.
The latter demonstrates one reason why we are "built like this". It's a very useful mechanism for survival, tool use, and agility. The former demonstrates one reason why our physiology is NOT "built for" for computer and office work.