Family is somewhat a biological construct. (You don't really get to choose what family your born into)
Now if a family endeavors to be some type of cartel or empire, it may qualify in that context.
Which ones do you specifically not see as a social construct?
(A person doesn't need the concept of society to exist to be wealthy)
What are the social constructs in Steem that led to it being what it is?
(You mentioned banks, there is a problem with 'risk processes' or types of 'gambling'
i explain it further here:
https://steemit.com/anarchy/@joesal/the-pareto-problem-and-capitalism
)