I generally do not wash before wear for my own items - especially outerwear or dresses which I feel washing might affect the shape of. I do wash all bras, underwear and sheets, though. I also used to wash my children's clothing before use, but now I generally do not. There are always exceptions, of course. Sometimes new denim really smells strange, and I will wash that before wearing, likewise with soft, under-jacket or cardigan t-shirts.
But I used to work in retail and the anti-EVERYTHINGS they use on outerwear are enough to outweigh any washing of regular items you might do. They treat outerwear - especially leather - with everything under the sun to keep it in good condition during shipping. Because these things are often shipped in huge metal cartons on ships and weather and conditions can be variable, leather is usually treated with anti-fungal, anti-pest, drying agents and more. They need to make sure that those items are not infested with insects, other creatures, mold, fungus or anything else before sale. Synthetic fabrics need less treatments because they are simply less attractive to insects and animals. Cottons and other natural fabrics need more treatment.