I Think You Are Delusional

Why are so many people delusional?

delusional
dɪˈluːʒ(ə)n(ə)l/
adjective
adjective: delusional

characterized by or holding idiosyncratic beliefs or impressions that are contradicted by reality or rational argument, typically as a symptom of mental disorder.
"hospitalization for schizophrenia and delusional paranoia"


I wonder what large group of people could be labelled as delusuional, if we really thought about it and put aside the social niceties....?