Why are there no annular lunar eclipses?

There are no annular lunar eclipses because of the relative sizes of the celestial bodies involved. An annular eclipse occurs when a smaller object passes in front of a larger one, leaving a ring of light visible because the smaller object is not large enough to cover the disk of the larger one completely.12

In the case of a lunar eclipse, it is Earth that casts a shadow onto the Moon. Because Earth is significantly larger than the Moon, its shadow is never small enough to create an annular effect where a ring of the Moon remains illuminated while the rest is obscured. Instead, lunar eclipses are classified as penumbral, partial, or total, depending on how much of the Moon passes through Earth's umbra or penumbra.213