This may sound snarky but I believe the reason is that traditional Asian martial artists spend most if not all of their time training students to defeat their own art. And it's tougher to defeat what you don't know or respect. After all boxing is inferior to art X, so why bother learning how to counter it, eh?
FWIW, These days I use modified versions of the Western ready stance.
True but also false IMO..
The reality is that if you train a method that has a particular strategy then most of the time training will be devoted to training that
You can't possibly train, especially regularly, with every other method so...... You focus on yours, your game and you do your best to implement that game..
These days most folks fight the same way IMO with small differences--soooo... There is plenty of opportunity to work with those who use the most common methods out there and tweak your strategy <Assumes one uses a primary strategy--positional/energy) For SD working the HAOV is doing much the same thing..
What makes some of these inside styles interesting is the idea of cheating and not playing fair whenever possible.. Folks can explore just how sneaky some of the moves are.. Cheat: time, space, energy and position as much as you can.
But today more than ever folks are cross training so it widens the spectrum quite a bit.