I'm curious why in dating sims some information is added that seems irrelevant.

Particularly "Blood Type"

I remember in Japan it had some relevance to personality.

Also what are the common bio info you'd see in a 2D dating sim? Eye color, weight, age, birth sign, as well as what else?

Personality? Humor? Occupation?

Dating Status, Height, maybe even throw in something like INT, STR, POPULARITY.

I know it's a rather small subject but I wanted to brainstorm the different stats to describe someone by their personality type in relation to a Social game.

It depends of the game, but dating sims typically give age, birthdate, blood type, height, weight and three sizes. For the female characters at least. Males are rarely introduced thoroughly, unless we're speaking about a more plot-centric VN instead of a typical dating sim.

Now you can have game-related stats for the main character, such as academic, artistic or sports ability.