Serial ports are still ubiquitous in embedded electronics. Crack open any non-trivial device and you will probably find a serial port, sometimes along with JTAG

Serial ports are still ubiquitous in embedded electronics. Crack open any non-trivial device and you will probably find a serial port, sometimes along with JTAG or SWD, on an unpopulated connector or on test pads, spitting out debug logs. And it makes sense from an engineering standpoint. Equipment for interfacing to a serial port, even in 2022, is widely available (you can get a basic TTL-level dongle for the price of a coffee) and pretty much every microcontroller/SoC has at least one hardware UART. If you want to see what your code prints to stdout while it's running on real hardware you could either implement a fancy redirection layer that sends logs over whatever interface your device has (and hope there are no bugs in it) or just use the built-in UART, wire it up to an off-the-shelf dongle and call it a day.