Why does the MRT break down so often?

I learned that the MRT system can breakdown due to
a) signal fault
b) track fault
c) power fault
d) train fault

I want to add the following:
e) passenger fault (why you all want to take train the same time?)
f) nobody's fault (the system just suka suka break down)
g) engineers fault (why you can fix the problem?
h) management fault (how can? we are top scholars! )