There may be costs to making things impersonal. Repeated interactions provide more opportunities to reward cooperation and punish defection, so the equilibrium

There may be costs to making things impersonal. Repeated interactions provide more opportunities to reward cooperation and punish defection, so the equilibrium point of a repeated game is often better than the equilibrium of a one-off game. Basically, it's sometimes more efficient to work with people you can trust. It's expensive to build protections that ensure people cannot betray you.