Why some of the people compares boxing & kick boxing? In fact boxing had no comparison with any other sport.?

Boxing originated from fencing techniques centuries before the 1800's and also used primitive wrestling techniques in the Old London Prize Ring Rules (you were even allowed to hug and throw your opponent onto the floor with the proper grip-clinch). When the Marquess of Queensberry rules were implemented in the late 1860's, they did away with all of those wrestling type of techniques and no-holds-barred tactics.

Very early throwback boxers from the late 1860's until the 1890's still had remnants of the Old London Ring Rules in their tactics (that's why their attack and defense was more linear {like fencing} and they tended to use an active clinch (inside arm wrestling to tire your arms and torso). Rounds used to go 20 or more. There were boxers ahead of their times that used a more modern arsenal of techniques but were also masters of those old linear tactics (Sam Langford and Joe Gans come to mind). However, more scientific lateral attacks and defense started in the mid 1920's (The start of the Golden Age of Boxing).

Boxing footwork is in actuality part of the techniques found within traditional stand up martial arts - it's just that those ancient martial arts have very complex techniques organized into long combinations using many parts of the body. But at their fundamental base (stance and footwork), there are many similarities to boxing.

After all, how many different ways of moving your feet can you create using the human body?