personally , reason not to use F14 is the weight. F14 is so much heavier than F18... and weight is directly affect the range and the turing.... i got a friend who is in the navy (Actaully alot of people asking why F18) .. everyone know F14 is superior than F18..but when in war F 18 is so much easier to catch up a F14... since F14 is "slow" in action... think about a F14 is runnig after the F18... when F18 make sereral turns, F14 is already fall behind...same reason with F15 and F16...
reason 2 cost..really is a big matter... especailly the engine... F14 engine is so easy to fail...and is so $$$ tp fix..18 is lighter ....
reason 3.... american tend to use ICBM or guilded millise now.... ( less loss in their army) and Use F18 as a support.... no need to have the superior power like F14