I didn't used to, but pretty much always, but especially if they are imported - which means most of them.
Many clothes are sprayed with formaldehyde to prevent things like parasites and mildew during shipping.
The cardboard boxes and pallets used for shipping are also quite heavily sprayed to prevent bugs, especially in wood, from being imported. I believe most pesticides used in organic fabrics are removed during processing, but I'm not 100% sure.