Shopify not charging in-state customers sales tax when the shipping address used is out-of-state

[Friendly1]

Please let me know why Shopify is not charging in-state customers sales tax when the shipping address they use is to a recipient with an out-of-state address. My business is only located in Arizona. My products are sent as gifts. Could someone please let me know why my in-state customers in Arizona are not being charged sales tax when they send our products to out-of-state recipients? For example, an Arizona customer purchased a $10 product to be sent as a gift to a recipient in Illinois, but the Arizona customer was not charged sales tax on the $10 product. Please let me know why Shopify is not charging in-state customers sales tax when the shipping address they use is to a recipient with an out-of-state address.