Lack of insight is common but not universal.
Quick Google search came up with this: Anosognosia - Frequently Asked Questions - Treatment Advocacy Center

"Studies indicate that 50% of individuals with schizophrenia and 40% of those with bipolar disorder report experience moderate to severe impairment in their awareness of illness. Anosognosia in bipolar is most common among individuals whose disorder includes psychotic features."

I don't know why I don't have a serious lack of insight.