Answer:
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see. What am I?
Skirts for men.
I am easy to see but no one likes looking at me. Without me there would be no you. I can make you complain or make you happy. But you almost always take me for-granted.
I come with a train and go with a train and the train doesn't need me but can't go without me.
the only amusing part of the body
The answer I give is yes, but what I mean is no. What was the question?