tbh I suspect it's at a fairly reasonable effort/reward point for them. There's so little you can factually learn from a short glance that confidence will always be low, and there are so many applicants (because applying is super low cost) that spending sufficient time to get a clearer answer is not worthwhile.

There probably are some high-quality-only recruiter groups out there, but they're not what most companies use. Which is probably why referrals are so valued in many places.