Anyway why do we need DO WHILE when we already have exactly what it does?
It is like putting a cup holder on your your cup holder..not really needed.
You are correct. You don't need it. 9900 Assembly language does not have structured loops... well... except in Forth assembler. :-)
But all of these things came out of the development of structured programming. It was felt by the experts like Dijkstra and Wirth that structuring things would get "spaghetti code" under control.
Maintaining commercial programs is a bigger expense than writing the code. It goes on for years.
Code that jumps all over the place gets hard to understand from the text of the program for the maintainer and is harder to modify.
So the structures that were common made you keep your loops localized.
FOR NEXT is one such structured loop in BASIC but you don't need it.
I remember that structured programming ticked off some people back in the day. They saw it as inefficient.
Dijkstra was clear on what he thought:
"It is practically impossible to teach good programming to students that have had a prior exposure to BASIC:
as potential programmers they are mentally mutilated beyond hope of regeneration"
He was apparently rather opinionated.