Because its that or find another job.
The Tomcat has never lost an air to air combat sim to an F18.
It was too big for the deck space, and required two to fly it. F18 was smaller and required 1 pilot. But the fist thing the Navy did was increase the size of the F18 and go to a two seat version.
It seems the only Tomcats flying will be those with Iranian colors. Oh, and I just loved the proposals for the QuickStrike, the SuperTomCat 21 and the AttackSuperTomCat 21, variants that were supposed to make the TomCat have a new lease of life (and make it even mroe lethal than it already ways). The AttackSuperTomcat21 -AST21- would have been basically bad-@$$. With twice the range of the F-14D, and note the F-14D has far greater range than any Hornet or SuperHornet that ever flew -and with capabilities that would have been second only to the F-22 in A2A, and unsurpassed by any fighter in the air2mud role. Obviously they cancelled since the TomCat had to die (had the SuperTomcat 21 come out several things would have happened ....for one there would have been no need for a SuperHornet, and secondly the JSF project would have gone the way of the A12 project. Thus it was a political stinky-poo and had to be cancelled).
Here is a drawing of the then-proposed ST21 SuperTomcat:
And here is an article questioning the prudence of replacing the TomCat with the SuperHornet. This is a rather interesting article:
http://www.flightjournal.com/articles/f14f18/f14f18_1.asp