That's where you're wrong I believe. Most servers now have at least one second incapacitation(or wounded mode) to stop bodies from flying around like godam rockets.I'm gonna go with what slayer said.
There are indeed subtle pools of blood, but thanks to the silly BF2 ragdoll effect, the corpses usually travel a bit before they come to a rest. You're just less likely to see the blood when it is not near a body.