Table of Contents styles should be able to take a selected page range, and generate a TOC based on only that page range.

Many books have multiple TOCs these days — a master TOC up front, and TOCs at the beginning of each chapter or section, and often a hidden TOC that is used to generate PDF bookmarks.

Being able to limit page ranges would mean less manually edited of generated TOCs, faster TOC generation, and needing to use fewer paragraph/character styles to handle them!