I agree. I really don't like Wilton Felder's bass sound, but as an A list LA session guy he must have been doing something right! Also I believe he used Precisions in the studio.
I guess it's the transistor radio/Dansette record player/car radio thing. The bass had to have a hard sound and be played up the neck in order to be heard, which is also why many players used picks on sessions. This sound is then softened a little in the final mix. These days most of us listen to our music on better players so the way the tracks are mixed has changed, and IMO improved.
Listen to I Want You Back, as it was released and they've mixed most of the "ponk" out and the bass sits shoulder to shoulder to the rest of the instruments. A good producer will listen to the track not the individual instruments.