Never got the hype for B-Spec if I'm being honest. In all the games it's been in, it's either been a cheap way to skip actually doing an event (GT4, GT6) or an excuse to massively bloat the career (GT5). Sure you could use it as a co-driver for endurances, but your Bob kinda just sucks at driving anyway.
Considering all the other experimental and innovative stuff the games actually succeeded in around that time (shuffle racing, seasonal events, community features), I'm surprised we don't get nearly as much nostalgia for those elements.