TC.
Heres a theory.
Initially the 500 ft rule keeps the novice uncomfortably near the cloudbase and then when the whiteout comes it is fear of CFIT and obstacles that stops them descending. The 500 ft rule was drilled into me as a student. Dire threats were made about what the CAA would do for low flying. And the low flying to avoid IMC would be deliberate.
My first excursion into the whitestuff (at 81 hours in a R44) was with a cloudbase of at least 600ft AGL! I didnt descend. I did a 180 and flew out of it as trained. Is the training an issue? Is this still what is taught? Its a few years since I trained.
Now, with a few more hours I'd descend and turn round or land.
Incidently, The CAA have made clear in a GASIL that they would never prosecute for landing to avoid IMC or any safety related issue.