If your eyeballs are missing, I can make an assumption that your vision isn’t great just by looking at you. That’s not a moral judgement.
Doesn’t mean blood tests are useless, and in fact it means we have some idea where to start investigating a potential health problem.
Yes, I agree that there’s bias against folks who are overweight, and also that there’s a range of risk associated with being overweight. It’s pretty clear, however, that obesity is a health concern that we should take seriously. If someone smokes five pack of cigs a day, I’m going to make an assumption about their lung health. There’s always outliers that live to 100 smoking and not doing exercise, but it would be a shit doctor if they didn’t tell folks not to follow their example.
This book speaks to it better than I can: https://theanarchistlibrary.org/library/david-graeber-bullshit-jobs/
Specifically take a look at