It's the eternal triangle of project management expressed for speaker development, the points of the triangle being;
- box
- xover and wiring
- drivers.
You want to make a profit on the speaker, but want it to stand out from the crowd, then you get nice veneer and quality drivers - but that costs, and cuts into profit.
So the xover gets shortchanged. Plus, most owners never see the xover, so it's a place to save money on.
I've upgraded most my speaker xovers, it's always an improvement.