There is no technical reason for this concept. It is more likely a result of the logical model that GCP uses.

In networking, most prioritization rules also follow this concept, where lower values are prioritized first. For example, when creating ACLs (Access Control Lists) on networking hardware, such as Cisco devices, the system evaluates rules starting with the ones that have lower numbers. Other vendors, such as Juniper and Palo Alto, also use this concept in their firewall. This approach is designed so that most network engineers can apply what they have been practicing in the field. On the other hand, it seems that GCP has chosen to use higher value to represent higher priority in Artifact Registry.