I believe it is actually BPH (beats per hour), unless I am not understanding your definition of BPS (guessing: beats per second).In physics, the ideal number is 57,600bps but due to the natural limitations inherent in the material used in watches, the maximum was determined to be 36,800, and with the built in errors associated with production that was further limited to 28,800. Many very good watches are operating at 21,600 but that is their choice. Manual wind, due to the losses associated with hand winding and the natural curve of diminishing returns(as the spring winds down)will often be no more that 18,600bps.
If the watch makers shifted to more exotic materials like ceramic/carbon fibre, they could achieve very close to the 57,600bps but Serrano's Law holds that for carbon fibre/ceramic to be viable it has to be at least 1mm in thickness so our watches would be quite large.
I think the accuracy of our automatics using the 28,800 figure is quite remarkable. Quartz, which has an oscillation rate 10 times greater that the spring used in automatics, can thus be almost loss free in it's accuracy. But then until the spring drive, quartz had to move in jumps, not smoothly, and this was an aesthetic negative.
Maybe in the future, we will find a material that will allow a greater bps.
we will see.