They are not commercial artists; they just want to share their ideas and entertain the travellers, because music always puts a smile on our faces.
They spend hours and hours playing their guitars and singing their songs. This is of great worth to them as they don't have a studio to record in.
There are lots of underground singer videos online of artists trying to promote themselves.
These stars have found a new place to promote amazing music.
Furthermore, American stars began to pop up on public transport.
Good luck with new projects for the beginners!