Why is not possible to nest forms in HTML

Answer 1

A form is a mechanism to submit data out of a html page by calling a different page. If you were allowed to nest them, it would not be clear for the browser, which form's action to execute.
There can be only one, as in Highlander. :)

Answer 2

But you can have multiple forms in an html document, just not nested.

Answer 3

This basically sounds like a very bad idea