Are health insurance companies hesitant to pay for non blood products? Is this the reason Doctors don't use them as standard practice?
Scully's post is correct, most often expanders are cheaper to use than blood. Blood goes through an expensive process to ready it for transfusion.
Contrary to what most people think, it is not physicians who are penny pinchers. They have some knowledge about the costs of supplies, but not in-depth. Their job is to treat the patients to the best of their ability, not to be concerned about a few hundred bucks the insurance might not cover (which is a drop in the bucket considering what a hospital bill costs).
Case Managers are more familiar with the specifics about costs and what each individual plan will cover, but I seriously doubt their input is a major factor in the decision to recommend blood vs. expanders, which most likely occurs in emergencies.
Keep in mind in the US there are thousands upon thousands of different health insurance plans, all with different coverage rules. (For ex, people think if they have Blue Cross it is the same policy nationwide, SO not true.) Physicians do not even try to memorize tens of thousands of ever-changing insurance policies.