For example there has been one man that always rides in and out of subway carts for the past two years. Last year he claimed to be a coach that wanted money for children, whilst this year he walks around with a box of twizzlers screaming his homeless and singing/ attempting to sing that a "twizzler a day keeps the monsters away". Whatever the story, each and everyday I generally see the same people. It's hard to distinct those who really are homeless, from those who are drug addicts. After once offering a lady lunch who sat outside CVS on a daily basis (midtown), and getting screamed at that she wanted money not food, I was most put off by her ungracious behavior. From that point I have been careful as to who I give money to.
While i was walking all the way downtown I noticed an old man who looked frail and ravenous. I walked about a block, before walking back to him and asking him if he wanted the two jackets to keep warm. His face immediately lit up as he couldn't believe what was happening. He asked me if I was serious twice and had a smile that I will never forget. He finally accepted the jackets while I walked away wishing him a Merry Christmas.
So my point here is that there are some people out there appreciative of items other than money. You just have to use your intuition and not give the man $100 singing/screeching "a twizzler a day keeps the monsters away".
Back to my main point of transportation in Manhattan, there are four main options: subway, bus, cab or feet.
When grabbing a cab in Manhattan, I always get inpatient knowing that I could walk faster than the speed they are driving at. Especially when the driver thinks you are a tourist and takes you the longest route possible, while the meter casually runs up.
I haven't quite taken a bus since I was a freshman in high school, but on behalf of those that do, I have heard nightmare stories.
Long story short: my theory is that walking is simply the safest mechanism of transportation, the easiest way to burn calories, and avoid lunatics trying to sell you stale twizzlers.