Why do we use RS232 serial ports to communicate with our hardware? Well, first and foremost, it is probably the least-common-denominator communication method in the industrial and embedded physical computing arena. If a computer has just one port, odds are it’s a serial port. This is mainly because serial ports are so easy to implement.
Those computers that don’t have RS232 serial ports, will usually have USB (another serial bus) ports. Because of the decades-long history of RS232, USB to RS232 ports are easy to find. Nothing wrong with USB, but it has more complexity and is limited to fairly short distances.
So, in a nutshell, RS232 serial ports are easy to work with, ubiquitous and reliable.