Why British guns retained pounder designations

Why did Britain describe some guns by projectile weight while the United States favored calibre and barrel length?

British terminology evolved from older cannon practice, and familiar pounder names remained useful until standardized calibre language gradually displaced them.

Terms such as two-pounder and three-pounder persisted because institutions and crews already understood what they meant. Standardized calibre and barrel-length nomenclature arrived incrementally, not through a single replacement of the older projectile-weight tradition.