Taste is changing, style is changing, and players abilities are changing.
We don't want other people poking into our artistic pie.
There are some sounds that English singers find quite difficult to manipulate.
Most Beethoven symphonies require 80 or more instruments, and the late romantics even more.
If the (British) Arts Council give you money, they also tell you how to spend it.
As you know, there are certain languages that lend themselves very easily to vocal use.