The guys who are 4* (or even high 3*) are the ones where there is enough tape and data on them for the various scouting services to feel pretty confident in them. We like to say that recruiting ratings are all about who is being recruited by whom...and that's an effect, sure, but mostly only at the lower end.
If a guy is rated in the top 1000 or so, that's less of an issue. And that's where we need to start playing. Because 3* and below, we turn 2.4% into NFL draftees. Above 3*, we turn 23.1% into NFL draftees.