Because when you're sending a signal down a wire or through the air, fundamentally the communication medium only provides "Send it, maybe it arrives" At any ti

Because when you're sending a signal down a wire or through the air, fundamentally the communication medium only provides "Send it, maybe it arrives" At any time, the receiver could lose power. Or a burst of interference could disrupt the radio link. Or a backhoe could slice through the cable. Or many other things. IP merely reflects this physical reality.