GS, a sonobuoy has a simple rotorvane or parachute. Add a guidance package and you increase cost, size and weight dramatically. The aircraft would have to tell the buoy where it is and where to go. It would need a guidance package and flight controls.
The issue is that at high level the buoy could be significantly further from its intended target due to wind drift but by dropping more then you hope to make up for that inaccuracy. Once it is drawing a target your next problem is locating the buoy's actual position. In the 70s that was more an article of faith than accuracy. (But the torpedo position was also relative
)
Another feature of early usage was the monitoring of the buoys. In theory, once contact was gained, the buoys closest to the target would be monitored. Around 1977 a modification to the Nimrod software gave the tactical navigator display an indication of which buoys were being monitored. We then discovered that the wet team was sometimes saying they were monitoring one buoy when in fact they were actually monitoring the wrong one. I wonder if any submarines escaped that way.