The most important text should look the most important.
Give titles a clear size + weight jump over body so the eye knows where to land.
When every number on a dashboard is the same size and weight, the user has to hunt for the one that matters. Make the single most important metric large and bold, demote the rest to muted supporting text, and the screen answers “how are we doing?” in one look. Size, weight, colour, and spacing guide the eye. More labels don't.
Visual hierarchy assumes there is a single most-important thing. On a neutral index, a settings list, or a glossary where items are genuine peers, forcing emphasis onto one is misleading, and even weighting is the correct choice. Scannable reference content wants consistency over drama.
An article renders its headline at the same size and weight as the paragraph below it. Readers arrive mid-page with no idea where the story actually begins.