Unfortunately, many of those young children and their parents live inside the Metro system, in any cubbyhole they can find. There are spigots that they use to keep clean, and some even have appliances so they can cook. The Metro police generally let them stay, unless there is some serious disturbance.
The people giving speeches in the Metro are beggars, who might have some mental or physical disability and have no other way to make a living.
The guys playing music are not supposed to be allowed on the Metro wagons, and I've seen them kicked off the train by agents. The only musicians allowed to play in the Metro stations have to pass a juried test and will have a permit to play in the corridors.