Reasons to not wash fabric (and other washable components) before cutting them
There is a sense of adventure in using unwashed fabrics -
The shrinkage may be none or a lot.
The bleeding may be none or a lot.
The chemicals may be none or a lot.
One can speculate about where the fabric has been and who has handled it before it gets to one's home.
Why take away the suspense of what may - or may not - happen to the item after it is washed?