Question

only some of the people on the daytime side of earth can witness a solar eclipse when it occurs, whereas all the people on the nighttime side of earth can witness a lunar eclipse when it occurs. why is this so?

Answer 1

Because the earth is much bigger than the sun

For a lunar eclipse to occur, the moon is in the shadow of the earth, (the earth is between the sun and the moon).

For a solar eclipse to occur the moon is between the earth and the sun.

The shadow of the earth will be much larger than the shadow of the moon - the lunar eclipse will be much more extensive, in size, than the solar eclipse.