Superman takes care of problems the human race appears unable to contend with on their own.
Even without evil geniuses and super-powered villains, though, Superman has the capacity to do things that humans have long struggled to do and are very expensive. For instance, he could launch all our satellites - a matter of hours for him to launch a satellite that would take weeks and millions of dollars for mankind. He could transport uranium waste into the sun and take care of human nuclear waste issues.
Doing so could lead humanity to depend on his assistance and would ruin any space programs or nuclear waste programs we are developing ourselves, limiting humanity's ability and possibly preventing us from growing as a species in some directions.
This is a relatively common trope for aliens visiting earth with plans to take it over - provide humans with something they can't easily do, create a dependance and level of trust, then that dependence results in weakness in the species that can be exploited.
What examples of increasing dependence on Superman leading to problems do we have?
What, if any, internal or external limitations does Superman have that prevent him from giving humans assistance that would result in damaging dependance?