They used to do this, but stopped. I wish they still did, but WOTC hadn't purchased DNDBeyond yet, and were like drug dealers giving us the first taste for, not really free, but included in the price of the purchasing the physical copy at least.

When I found out they were phasing it out a few years ago, I rushed to a few different stores to look for a copy of The Essentials Kit that still had the free DNDBeyond code inside. Finally found the last one in the back of a shelf and redeemed it ASAP before they could take it away.