Why does a 1 TB drive show less capacity?

Vendors often label decimal TB/GB while many OS tools report binary TiB/GiB, so the number looks smaller.

GB to GiB Converter – Decimal gigabytes to gibibytes

1 GB = 10⁹ bytes and 1 GiB = 2³⁰ bytes (1,073,741,824). Divide GB by 1.073741824 to get GiB. A marketed 128 GB volume is about 119.21 GiB.

How many GiB are in 1 GB?: 1 GB ≈ 0.9313 GiB.
Why does a 1 TB drive show less capacity?: Vendors often label decimal TB/GB while many OS tools report binary TiB/GiB, so the number looks smaller.