It's 8086's history as a descendant of a limited 8-bit ISA that made it lack PC-relative addressing. I'm not sure why it was never added in all of its iteratio

It's 8086's history as a descendant of a limited 8-bit ISA that made it lack PC-relative addressing. I'm not sure why it was never added in all of its iterations until x64. Other ISAs from the minicomputer age (PDP-11) and their descendants and inspirations (H8, 68k) had it. Zilog added PC relative loads and address calculations to the Z8000, and it's a generally popular form now in x64. The Unix V6 assembly source code is very readable because of this and also I think it was unfortunately responsible for the 0-terminated string use because of the ease of writing it that way.