Hello,
Products with a weight are product with shipping required.
When the shipping is required, the shipping address is asked.
And legally in most countries, you must have a billing address for every order.
Afterwards, it is possible in HikaShop 3 to dynamically change the checkout workflow via a plugin.
So with some development, you could remove the "address" block from the workflow when the order total is free.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.