Closing tag in XML

I always wondered why they didn’t allow an optional closing tag of “</>” that would close the corresponding open tag.

For example:

<p>This is a string with something <b>bold</> in it.</p>

where “</>” is closing the <b> tag. Or:

<blah><bleh><blih><bloh>bluh</></></></>

which is shorter than:

<blah><bleh><blih><bloh>bluh</bloh></blih></bleh></blah>

I fell it is a shortcut like the stand-alone tag <tag/>.