Why isn't the semicolon a reserved character?

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

This XML document is not well-formed:

<Document>
        ]]> 
</Document>

Why? Because the XML parser see that and thinks that the > symbol marks the end of a CDATA section; the XML parser throws an error since there is no preceding <![[CDATA

The > symbol must be escaped like so:

<Document>
    ]]&gt;
</Document>

Now consider the ; symbol. It marks the end of an entity reference. 

This is a well-formed XML document:

<Document>
    A;B
</Document>

Why doesn't the XML parser see that and think that the ; marks the end of an entity reference; why doesn't the XML parser throw an error since there is no preceding & symbol?

Why isn't the ; symbol a reserved symbol? 

/Roger