Yes, I have wondered about underreporting too but it would have to be a remarkably far-reaching phenomenon if so.
My day job is in tech but my background is in law and I advise pro bono as I have throughout my legal career on a regular basis at an advice clinic. This advice clinic essentially says "come to us if you think you have a problem and we will tell you whether we can help". That means that probably 50%+ of our cases are things that we can't help with (as there is no legal issue there) who we turn away. What that also means is that we also see every single person who can be bothered to come to us of an evening and therefore get a very wide aperture view on the problems that people have in their lives, both legal and non or sub-legal, in Southwark, Lambeth and sometimes farther afield.
What has also been suggested to me is that black people in particular have a special distrust of authority that makes them unlikely to seek legal advice of any kind at all. That has always struck me as an odd argument given that probably 40-50% of our clients are black and are more than happy to come to us to discuss housing, immigration, benefits employment etc...