Why India needs Red Light Area?

India has become the largest market of human trafficking and sex trade. In every state there is "Red Light Area" in Kolkata there is "Sonagachi". Why? Why country need them?
Why no government demolish these areas?
There's another big question of how and where to put those sex workers because society ban thz women. We call them prostitutes, sluts, sex workers and many insulting words but do they deserve that. For me they are the bravest women of world who face various demons in human form and no one takes there complaint.
Think about rapid rape incidents and solutions....
Govt should put these brave women on streets as civil police, taxi drivers and various related services at night to protect us. What you think abt that? I strongly feel if there's no such red light areas in country many children and gals can be saved from human trafficking.
But question is " Why its not on any governments plan?"
" Why NGOs who are trying to help these women face dead threats?"