RS232 and DOS
DOS and PC BIOS Support for RS232 was almost non-existent. Being a single threaded OS The BIOS interrupt you were supposed to use would hang the whole computer, also it could only support sending and receiving 1 character at a time. It didn't matter if you were C, Pascal or Basic you had to do it in assembly if you wanted to do it properly and you had to dig out the technical manual out and write your own interrupts. No stackoverflow in those days so most people wrote and suffered the BIOS call. Also a reason lots of old industrial programs would not work properly under windows.
Biting the hand that feeds IT
