Maybe it's because the most recent version might be more familiar to viewers*, but if you're going to use the old-school logo, why not just use the 80s set?
*I question that, seeing as how when the show is parodied on shows like Family Guy and Robot Chicken, they use a mock-up of the 80s set. I mean, yeah, Donnymid's the most recent version, but it's a bit obscure as a pop culture memory, compared to 80s Pyramid with the massive pyramids everywhere. You know what, nevermind, why am I questioning Ludia?