The data shows correlation, not causation. I can think of at least two causal explanations that would account better.

1) Children born to wealthy parents are both a) more likely to go to college because their parents can pay for it, and b) to step into high paying jobs because of their social networks than poor kids. Thus while there is correlation between college degrees and earning potential, the root cause is being born into a wealthy family.

2) Smart people are more likely to go to college than dumb people, and smart people are more likely to do well in jobs which require intelligence. Similarly, intelligence is the causal factor, not simply attending college.

College may very well be worth the money; but your statistics prove no such claim.