Isolated bass tracks are never meant to be heard in isolation. Criticising a bass player's technique or whatever is just pointless, as the end result is all that is intended to be heard. And if that sounds good, then it IS good. It's all the little nuances, rattles, timing errors, pushing and pulling and even mistakes that make great bands great. It's not just the bass doing this, it's every member of the band and it's what makes music like this greater than the sum of its parts. As already said above, this is why modern programmed digital music has no soul because it's perfectly produced and perfectly in time. It has no humanity about it whatsoever and relies almost entirely on production tricks to make it in any way interesting.