Some bass guitars have their pickups close together, why is this ?

I haven't noticed that before. Just guessing here, but maybe there's not enough useful tone on that particular instrument near the bridge to warrant a pickup.

For tone.

"This Hofner" is the "Cavern Bass." The one McCartney played before the Beatle became famous. By the time they made the big time, he was playing the more modern one with the pickup moved closer to the bridge.

    I’m thinking that in the environment of contemporary technology improvements are added with a tendency towards linear results rather than parallel.  Likely addressing a function rather than an overhaul redesign. With the amplification that was available, which was good, tone was more a consideration at the amplifier, a bit of tone (treble bleed) and primarily volume at the instrument sufficed, getting a stronger signal to the amplifier was likely the reason for the second pickup, in it’s initial application.

    In a redesign, the abstract of distancing the pickups may have reveled more tone variation onboard the instrument, which obviously would be an improvement. Probably not as relevant for bass as the guitar. I still love the tone I get from my old Precision with the single pickup, though my goto is the Guild Starfire.