It's because the old logo was properly created by some ad agency to pass the idea of the "Yahooooo" sound.

Hence the best logo chosen by the people (which i think is not the official word by yahoo inc) also has that "feeling".

All the logos with a fixed baseline, or jagged baseline that goes against how western read the "yahoooo" sound, just feel like you changed the font in MS Word and typed Yahoo!. Which is all most of those are...