The way I've heard it explained, there are some historical alternate versions of some characters (A Latin-alphabet equivalent might be the way we sometimes draw

The way I've heard it explained, there are some historical alternate versions of some characters (A Latin-alphabet equivalent might be the way we sometimes draw "a" with an extra curl across the top, and sometimes without) that have the exact same semantic meaning, and so they were 'unified' to a single code-point. Unfortunately. some people spell their names exclusively with one variant or the other, and Han unification makes that impossible in Unicode.