Sometimes the thing that seems obvious, is just not worth the effort. Means testing is often the case for this. Consider: Medicaid and Medicare in the USA cost the same as the whole of the UK’s healthcare system, even though they only cover select groups*.
Similarly, free college is not worth means-testing. This is only a short article because I wanted to draw your attention to this interesting piece by Christopher Keelty: On free college for billionaires.