there must have been some sort of explosion of obscure pedal systems in the 70s or something
Later than that (between about 84 and 94, Shimano went through a clips-n-straps pedal with a semi-locking cleat [7400], a licensed Look copy with decent bearings [7401], SPD with cleat pontoons for road racing [7410] and SPD-R [7700] in quick succession). The reason why people have stuck with SPD-R is not that they couldn't afford to modernise, or that they like the retro look, it's that SPD-R was and is the apogee track clipless.
Meh, I bought a set and drilled some sidis to fit them when I started working at the velodrome, wasn't overly impressed but given that everything was used and could have been worn out, I'll give the system the benefit of the doubt.
Later than that (between about 84 and 94, Shimano went through a clips-n-straps pedal with a semi-locking cleat [7400], a licensed Look copy with decent bearings [7401], SPD with cleat pontoons for road racing [7410] and SPD-R [7700] in quick succession). The reason why people have stuck with SPD-R is not that they couldn't afford to modernise, or that they like the retro look, it's that SPD-R was and is the apogee track clipless.