Because maybe you’re thinking, “Oh, well, I don’t need to wash it, it’s totally untouched so it must be safe!”
Just like new underwear, a sex toy should be cleaned thoroughly with mild soap and hot water after you take it out of the packaging and let it air dry on a clean surface. Sex toys are not sterile, so it’s reasonable to expect that they have dust or bacteria, even if brand new.
The good news is that many sex toys are waterproof. But, before bringing a toy in the tub with you as a bath-time companion, always confirm that it is safe for submerging.