The easy answer is that the HD video specification (ITU-R BT.709) only has what you call broadcast limited.
The longer answer is to understand what it’s for. It gives you headroom for video processing and exposure changes. If you don’t have any headroom, then you get clipped highlights. If you have clipped highlights, then any further filters (including those used in the encoding process) will cause artefacts known as ringing - Ringing artifacts - Wikipedia
For a fuller overview: