AB+ are all "blood is blood", but nobody wants their shit-tier dodgy blood!
AB+ Gang rise up. Universal recipients (sigma parasite) and universal plasma donors. When receiving blood sometimes I'll mix A, B, and O just to flex.
Years ago I read somewhere that they discovered a way to remove something from the blood and make it universal, like eliminate blood type all together.
Wonder how that research going?
It's expensive and blood can only be stored for so long. Easiest to stick with compatible blood types.
There are also loads of other antigens in blood that can cause a reaction. These are just the commonly known ones. So blood should still be cross matched anyway if it isn't an emergency.
And, quite frankly, we actually are getting somewhat close to producible artificial blood, so there's just not a whole lot of need for the investment.
And those artificial blood studies have DARPA money behind them.