- Even each instruction does a lot of work, it is supposed to do it in parallel, so time available to fetch the next instruction is (supposed to be) the same.

- Not everything is parallelisable so most of instructions words end up full of NOPs.

- The real problem are data reads. Instruction fetches are fairly predictable (and when they aren't OOO suck just as much), data reads aren't. An OOO can do something else until the data comes in. VLIV, or any in-order architecture, must stall as soon as a new instruction depends on the result of the read.