Why seaplane carriers were not convoy escort carriers

Did seaplane carriers escort convoys during the Second World War?

Generally no. They were used to support seaplanes and flying boats as mobile aviation bases.

Seaplane carriers existed in significant numbers, but they were not normally the aviation ships placed inside convoy formations. Their work was to support seaplanes and flying boats and act as mobile bases for those aircraft. That mission kept them outside the escort-carrier story even though both ship types supported naval aviation. The distinction is operational: tending aircraft elsewhere is different from carrying a convoy's own fighter or anti-submarine detachment.