Why http is asynchronous?

Answer 1

HTTP is a text based protocol for exchanging data over a network, and the preferred protocol for the internet (a.k.a. World Wide Web)

HTTP is synchronous: a client issues a request and waits for the corresponding response before anything else is done.

Asynchronous Javascript And XML (AJAX) is a way of using a HTTP request from the web browser to retrieve data using JavaScript, without leaving the current page. This use is said to be asynchronous because the JavaScript is making the HTTP request does not wait for the response, but instead continues any further necessary processing. A handler function is called to deal with the response, as and when it arrives.

So the real answer to the question as it stands is: HTTP is not asynchronous.