The answer to 'why is my carpenter ant bites' is that carpenter ants do not actually bite. Carpenter ants have strong mandibles (jaws) that they use to chew through wood, but they do not have the ability to bite or sting humans. The sensation you may be feeling is likely from the ants crawling on your skin, which can sometimes feel like a pinprick or irritation, but is not a true bite.
Carpenter ants are attracted to damp, decaying wood and often make their nests in the walls or structure of a home. While they can be a nuisance, they do not pose a health risk to humans. If you are seeing a large number of carpenter ants in your home, it's best to call a professional pest control technician to properly identify the issue and recommend treatment options.