We don’t think linearly (we’re extremely parallel) and computers don’t think exponentially (just quickly, ironically enough that’s because it was easier to run ten times faster than on ten things at once).
To get more pedantic technically doing things in parallel is easy - coordinating them is a pain with overhead - especially if you want them to keep their speed. I know back decades ago even cars went with plenty of microcontrollers to do what technically could be controlled by one since it was easier and better to be independent apparently - and auto companies are all about shaving nickels of expenses for profits.
