Yes good question.
This used to be quite the norm in the past... with every type of highend speakers, there were always two sets of speaker terminals. This was largely due to that "stage effect" that everyone was trying to create. Or should I say, recreate a stage effect in the home. I refer to it as a stage effect, simply because it's much louder, has more force, impact and dynamics but no musicality. Lacks intimacy, immersiveness, and is musically dis-engaging. At least for me it is.
Now, if you look at the majority of highend speaker systems, the real top stuff, they in fact only have just one pair of inputs. The designers also experienced the associated problems with added distortion and phase issues when it comes to adding cross-overs... on top of crossovers that are already built in. They looked at keeping things pure and simple, shortest signal paths, least amount of connection points, executed with the highest quality parts yields far better results! They discovered the sound and purity of source signals to be superior, and uncoloured.
Bi-amping, bi-wiring adds more things into the mix and makes things more complicated. For better channel separation, minimal cross-talk and superior dynamic drive, monoblocks are the answer. However, a very well designed high powered Class A designed stereo power amplifier, is just as good. Monoblocks aren't required.
Speakers have also become far more efficient with easier loads to drive, compared to those days... and this has been the trend, so I wouldn't even think of bi-amping. I've done so in the past with several versions of Maggie's and Apogee Diva's that I previously owned but none were of success. Either single stereo amps or monoblocks were far superior. It was a much cleaner sound overall. There was more of the music flowing from good recordings.
Just my 50cts worth...
Cheers, RJ