Ummmm... Really?
Crossover filters, even relatively steep slopes, are just that... sloped. There is a curve. Acoustic energy radiates from both pass bands for roughly an octave on the "downhill side" of the crossover.
And while really steep slopes may "seem" like a good idea-there are issue that come along with them-such as ringing-additional delay and so forth.
It is not always a "free lunch". You often have to choose between the lessor of 2 evils. And until you look deeper-you may not actually "see" the evil that lurks within. Kinda like politics-but I don't want to go there.
Of oucrse you can just simply choose to "ignore" the facts (just like in politics)-but that does not mean that it isn't there.
Kinda like comb filtering. Just because someone can't figure out how to reduce it-does not mean it is not there and does not affect the overall performance. But there are better ways-just maybe not in their current toolbox.