Sadly, you need to prioritize certain types of data over other types of data. For instance, if that bits that make you your cute cat picture show up out of order, late, or need to be retransmitted, it isn't really a big deal. However, if the packets making up your 911 call show up out of order, late, or need to be retransmitted, someone could quite literally die as a consequence. That's why we have things like DSCP marking. Different services, by definition, need to be given priority over other services based on their intrinsic characteristics.