The Voice Control feature we know today has lineage in Apple history. One of the banner features of the iPhone 3GS, released in 2009, was Voice Control.
The official reason Apple created Voice Control is to provide yet another tool with which people with certain upper body disabilities can access their devices.
There is also opportunity for Voice Control to have relevance beyond the original intended use case. It might find appeal to people with RSI issues, as using one’s voice to control your machine would alleviate pain and fatigue associated with using a keyboard and pointing device. Likewise, others might simply find it fun to try Voice Control for the futuristic feeling of telling their computer to do stuff and watching them respond accordingly. Either way, it’s good that accessibility get more mainstream exposure.