Simply because the pi isn’t x86_64. You wanted this thread Installing Home Assistant Supervised on a Raspberry Pi using Debian 12
As it says in post 1
This guide will help you to install Home Assistant Supervised, on almost any machine type you choose. This guide has been tested on machines including a Lenovo m72e, Dell Optiplex SFF 990, Dell Optiplex USFF 780 and a HP T520 thin client. If you are using a Raspberry Pi , follow this guide.