Separate loudspeaker drivers like separate electronics maximize the attributes of each: amplifiers focus on amplifying, sources are specific to their task.
And so it is with speakers too. No woofer can reproduce that which a proper tweeter can. Take for example the planar tweeter in the upcoming FR30 loudspeaker. Its moving diaphragm has lower mass than the air it is driving. Try that using a heavy-high mass woofer. Or the opposite. The thin planar driver is no match for the long-throw woofers used to pump long wavelengths of bass frequencies into the room.
In my opinion, there's simply no substitute for separates whether in the multiple drivers that make up a loudspeaker or the multiple boxes that together produce music that brings us pleasure.
If high-performance and precision are the desired outcome, then it makes perfect sense to maximize one's assets.