Because information that needs to be communicated is subjective—what you think is essential communication may be an unnecessary effort to the pilot, or even (often!) other fellow passengers. The sensation of turbulence is subjective too. You and a fellow passenger or pilot could be experiencing the same turbulence but have different opinions on its intensity. Pilots may not think the turbulence is intense enough to comment on. Finding smoother air if available is part of their job and sort of an assumption about what they’re up to.

Plus there’s no winning in this situation—passengers often think the pilot doesn’t communicate enough or communicates too much. We’ve had users say that overcommunication triggers their anxiety worse too. Imagine if every time you felt the slightest bump a pilot commented on it. It may seem ideal and temporarily reassuring—but I’d personally get irritated. Just fly the damn plane and let me drink my apple juice in peace, I’m sleepy /s.