Why is Optical Zoom on High Definition Camcorders (10X) typically less than standard camcorders (25X or 40X)?

Question

Why is Optical Zoom on High Definition Camcorders (10X) typically less than standard camcorders (25X or 40X)?

Answer 1

High definition camcorders generally have larger sensors (needed to fit on the extra pixels) the effect of which is a focal length reduction.

The other issue is that high definition will show off any flaws in a lens more than standard definition, especially as you zoom in and use the central 5% of the lens (as would occur on a 20x lens)

Be assured that 10x zoom is actually massive, anything beyond this becomes very hard to keep steady, even on a tripod, and the greater the zoom the more light you lose through f-number drop.