#1 is the biggest reason. Much of UK1-2 and US1-3 has to spent on navy, and as you point out there is no way around that.
It also takes the US at least 3 turns to just set up their shuck-shuck to get troops to Europe, which means you don’t have to worry about the US in significant numbers until about rd 4 (at the earliest) or rd 5.
The problem is once the US is set up they, with the Brits, can land anywhere from 14-16 units in a number of Germany territories. That number can increase up to about 20-24 if the Allies can afford to go to WE.
Now, battle losses are important, but it terms of sacrificing economics, position is vital, and you are dead on with a “center of the board” focus.
Although, one final thing I would consider is supply lines.
In terms of our game I think much was sacrificed by the Axis in order to “blitz” to Moscow. Now you really had no choice, due to the the G1 turn in Afr but assuming Russia holds out for another turn or two, I think the Axis are going to be in real trouble. Not that Ger or Japan will fall soon, just that the opportunity to take Mos will close.
Well, at least I’m hoping it will close. :-D