Freezing cells is difficult, almost an art form. It depends largely on the types of cells being frozen, the program to be used in freezing and the program used to thaw. You can end up with a massive loss in viability if a technician doesn't follow a freeze or thaw protocol to a tee, and there are release criteria where products of low viability cannot and should not be infused.
Being said, cryopreservation of blood for transfusion **exists**, and has since the Vietnam war. We're getting better at the process, but barriers such as cost and training probably still pose a hindrance.
Another barrier is maintenance of stocks, especially if you're considering monitoring your own blood supply. A cryogenic freezer would need to be maintained and monitored for constant -160-170°C. Cells do not undergo multiple freeze-thaws and thus once thawed you have a short shelf life.