An advantage of names in end tags is human readability. Consider this XML fragment:
<a>12<b>34<c>56<d>78<e>90</e></d></c></b></a>
Appending something to the end of the d element is easy, since one can just search for its end tag. In JSON and other formats that only have one single character at the end, one has to count brackets or parentheses for this purpose:
If they're all <a> then you're back to square one.
JSON solves this with indentation, pretty printing, and using paired symbols that most conpetent editors can automatically balance. This solves the homogeneous case too.
Incidentally, XML can benefit from the first two, and many editors balance tags, so you can get the same thing there.
No, there were a couple of layers in that case. But that doesn't actually help you add a child at the correct level, because the end of a contract would look something like:
