Do all patients in a facility need a CBC or BMP drawn? No, but doctors in the ER tend to order them as a shotgun test. And those also include a glucose level. It's a noninvasive diagnostic procedure. You're not administering a drug just for the hell of it. Comparing it to oxygen administration is kind of apples to oranges.
Just because it does not harm the patient or carry any significant risks does not mean it's good medicine. It's still poor medicine to use ANY resources that you don't need to on patients that have basically no indication for the test or intervention. I hate that hospitals draw CBC's and BMP's on everyone, including the patient that was here 14 hours ago for the same complaint...