We usually mistakenly believe so because of pluralistic ignorance. See: https://en.wikipedia.org/wiki/Pluralistic_ignorance#Research
Pluralistic ignorance and alcohol use on campus: some consequences of misperceiving the social norm (1993) — https://pubmed.ncbi.nlm.nih.gov/8433272/
We usually mistakenly believe so because of pluralistic ignorance. See: https://en.wikipedia.org/wiki/Pluralistic_ignorance#Research
Pluralistic ignorance and alcohol use on campus: some consequences of misperceiving the social norm (1993) — https://pubmed.ncbi.nlm.nih.gov/8433272/