Many hardware devices and operations take time to finish. It therefore makes sense to choose asynchronous actions using interrupts and timers instead of blocking operations.
When doing bare-metal programming, you'll tend to use a single loop with interrupt routines and timers that allow you to respond to and poll for events. If programmed in a fully asynchronous manner, this main loop will efficiently work through the tasks while the interrupt handlers update the data that has to be processed.
Even on SoC platforms, the use of asynchronous methods is a good idea, as things such as network operations and other I/O operations may take longer than desirable. Having ways to deal with operations not completing is another issue that pops up.