Heck, even if it is covered, you don't know how much is covered. One of my former coworkers needed a test to rule out $SERIOUS_DISEASE. She had the company's health insurance, which was pretty good insurance, but she wasn't sure if the test would be covered, and if so, how much. She was fresh out of college with little savings, so spending a bunch out of pocket for a test had to be carefully planned. So she tried to find out how much it would cost her. The lab said "up to $XXXXX depending on how much your insurance pays for, but we don't know how much they'll cover" she called the insurance and she was told to talk to the billing department at the lab, and she eventually got in touch with the billing dept at the lab which said "$XXX (probably)". I listened to her call people all day to find the answer to a simple question and get several different "maybe this much? we don't know until the bill is submitted" answers.
She was really upset that it would still cost so much - but when she explained the situation to other co workers, they said it didn't make sense, it should be fully covered. She didn't believe them, and almost cancelled the test (chances of $SERIOUS_DISEASE was low). Eventually someone convinced her to just get the test. Turns out it was fully covered, which was a relief to her, and the test was negative. But it amazed me that should could not, for the life of her, get a straight answer as to how much she was going to have to pay and the potential of the cost of the test being so high was a bigger issue than the possibility of having $SERIOUS_DISEASE