What is the main reason that restaurants, offices, and other public places have separate areas for smokers?

Ihave a really high metabolism and only weigh 70 pounds (13 almost 14). people always ask me two questions: do you ever eat and how do you eat so much and stay so skinny.i am worried that a high metabolism wont me forever. what are some safe steps i can take to maintain being fit. (also, i already work out i am a dancer so i get cardio a lot)

How can people get cancer? what types of cancer are there? plz i’ll mark u brainliest

Asubstitute is standing at the halfway line waiting to enter the match at the next stoppage of play the ball has gone over the touchline for throwing and referee allows for the substitution to substitute wants to take the throw-in does the substitute first have to enter the field of play before being allowed to take the throw-in