i have noticed it too, but you aren't watching it close enough.
crash and spyro were made by naughty dog and insomniac (love them both), but OWNED by universal. so when crash and spyro came to ps2 they were made by other developers. jak and daxter and ratchet and clank are owned by sony, but still developed by their studios (hopefully jak will be). this means that they will both be great series.