Why are underrground railoways in New York City called dirty and obsolete? Many homeless people and beggers choose to live or stay there.

I don't think those photos are representative of the current or normal everyday condition of the NYC subways. Have taken the subways for many years for work prior to the pandemic and not seen what's depicted in those photos. That being said, the homeless crisis has gotten worse over the years. Hopefully a new mayor next year will bring a new administration with fresh ideas on how to improve things.