I began washing my fabrics when I found out that they spray the fabric with bug killers when it is imported into the country. Much of what we use is imported without knowing it. I for one do not like the idea of handling that chemical daily.
I do wash mine. Especially batiks because of the dyes that like to run from the process they use.
But, if you want to just test a small amount to see what it will do when washed, that could save you hours of ironing if you are in a hurry and the quilt isn't an heirloom in the making.