@Iragersh maybe not in NYC, but SFMTA (San Francisco) has racks on all lines (https://www.sfmta.com/getting-around/bike/bikes-muni)
I suspect hills may have something to do with it😃
Combining bikes and Muni is a great way to get around San Francisco. Whether you’re putting your bike on the bus for a fun ride in Golden Gate Park or Treasure Island, or using it for your commute, bikes and Muni are a perfect travel combination.[VIDEO::https://www.youtube.com/watch?v=MJT2IENe8d4::aVideoStyle]Basics of Bikes on MuniBuses: Every Muni bus is equipped with two or three bike racks on the front of the vehicle. Full-size bikes are allowed on bike racks.
NYC Glue
Paul Wermer, CC BY-NC-SA 4.0