this is why you got dropped

Either 1) you didn't show off enough of your personality/interests for girls in a house to know if you would be a good match, and other girls did so they got higher scores 2) girls in the house didn't remember meeting you when it came time to vote. They are talking to 3-5 girls per party and have to remember their first and last names. They are talking to girls all day. Even if you were pleasant enough, you have to also stand out to them to get higher votes. 3) They thought you were awesome but they thought other girls were even more awesome. 4) You connected with one or two girls in particular but they didn't think that you would vibe well with the general culture of the house. They consider what the entire chapter would want when they vote. 5) You came across as rude in some way.

The system does NOT 'make mistakes'. Girls who are complaining about not getting a certain house are literally saying that they are 'better' than every single girl in that house's pledge class. Houses know what they are looking for and they will find it. This includes not giving bids to every single girl that goes through rush, because that would be insane. If a house does invite you back, that means that out of the hundreds of girls that they saw that day, enough girls remembered you and thought you would make a great fit with their house. If you decide to throw that opportunity away because you feel entitled to a particular house, that's on you.