In cishet majority social situations, people are rapidly sorted into the men and the women, the he and she. The apparently obviously gay are also picked out based on stereotypes. Anyone in a relationship is assumed monogamous. For those not falling into these buckets or incorrectly assigned, the work begins.
Bisexual people can wait until someone mentions dating and share their own stories, strategically traveling through genders their dates had. Dating stories also provide an opportunity to mention nonmonogamy through any inevitable misunderstandings that have arisen when meeting someone for the first time.
Trans and nonbinary people who have been misgendered can allude to the pervasive transphobia in the media, state their correct pronouns, and escape to the bar for a bit. They can try to anticipate and prevent any awkwardness with the people sitting closest by introducing their pronouns alongside their name. But after a few drinks, people aren’t always able to notice or remember these details.
Cishet monog people get this gender, sexuality, and relationship orientation sorting out of the way automatically. Kahneman would call it System 1 thinking, which is very fast and sometimes very wrong. Enter any variations from the cishet norms and more energy is required to establish the basics, and often to try to explain what it all means.