Depending on if you are really asking whether there is an advantage to active pickups or active basses (which as mentioned are generally passive pickups and a buffer or preamp), the initial (and still the best) purpose is to reduce signal loss going to your amp.
If you have an active bass, the signal created by your pickups is sent to your amp. If you have a passive bass, the signal your amp gets is the signal of your pickups and all the wiring that goes between you and your amp (or effects), so you tend to loose the high frequencies quite a bit with such a circuit.
Also because the output is a low impedance, you have less noise injected in your cables on a long signal run.