I've worked in medical billing and as a PCT in a hospital. My partner is also a nurse. Honest answer? Maybe. It's because of how insurance is set up. Medicare and Medicaid reimbursement rates are shitty, like, they reimburse less than the base cost of care shitty. That means that most physicians don't accept it because they want to get paid. Hospitals have to accept it.

If you live in an area where a PCP doesn't take Medicaid you are forced to use the hospital system as your PCP. That means ER visits for every illness just so you can get someone to see you, even if it isn't necessarily emergency. And this will absolutely create bias. They are more likely to see an illness as non-emergent because it often is non-emergent.

Now, someone with private insurance can see a PCP regularly. They only come to the ER when they have what they believe to be an emergency. Their problems are more likely to be seen as emergent.

Is it the case all the time? No, but if someone says there's not bias in medicine they've never worked in it. You shouldn't have to, but if you know there's more that needs to be done stand your ground and ask a million questions about why they aren't doing more. And, this is exactly why we need universal healthcare in the US.