It's extremely common to use both cores on the dual core Xtensa because you can bind ESP tasks (WiFi/Bluetooth) to one core and schedule your application code o

It's extremely common to use both cores on the dual core Xtensa because you can bind ESP tasks (WiFi/Bluetooth) to one core and schedule your application code on the second core, reducing jitter visible to the application code. The cores were even named Core0 - PROtocol and Core1 - APPlication in the initial ESP-IDF design, where the core affinity model was going to be more strongly enforced (thankfully they backed off on this idea and now it is fully configurable SMP).