One hit the HMS Sheffield, two hit the merchant ship Atlantic Conveyor, and one hit the destroyer HMS Glamorgan. So that's 4 of the 5.
I think they just ran out of missiles.
Edit: even if France supported the UK during the war, preventing the delivery of more exocet missiles and providing information on the missiles and airplanes to the UK.
Edit 2: Apparently it was an oversight, the French team in Argentina was never told to stop working. Also I guess the missile builder might have been happy to have a live fire demonstration of his products
To be fair, Israel also advised Argentina on air-to-sea surface attack tactics that proved to be seriously good.
There's no denying their effectiveness in this example, but then the context was the UK was fighting a conflict halfway across the world and without air superiority. Take away either of those elements and the Super Etendards were likely to have been obliterated long before their Exocets were within range.
Furthermore, waiting would have meant the islands would have entered Antartic winter shortly after invasion, giving them many months to dig in and prepare for UK Task Force landings.
There where probably career officers raising all the issues you did and more but it didn’t matter.
It’s interesting to speculate what thatcher would have done had the Argentines managed to sink enough ships to end the first Task Force, we where already fighting at our limits (which showed just how poor our equipment and spending was, lions lead by donkeys still applied), force project is hard, force projection for a 2nd rate power (if we class superpowers as 1st rate) at best is ridiculously hard.