I'm not sure I totally agree with you historically, though. Britain is a rare exception. Germany won was the aggressor in almost every war it fought post Napoleon, and they always mobilized highly. France probably suffered more from Napoleon's wars than they did when Germany invaded them in 1870.
The historical level of sacrifice does vary. It partly depends on your definition of sacrifice for "the rest of us." Most wars are small enough that only the standing army is involved and the population hardly notices them (granted, these are the small ones that the history books skip over). The impacts scale up from there to increased taxes, shortages of goods, mass conscription, having bombs dropped on you, and having enemy troops come to your home. The last generally only happens to the losers of wars. Winners can see any or all of the rest of the list but few wars have major strains on the winner's society. Viet Nam was fought without putting any of those demands on the US.
Wait, rereading your post....why is "offense" associated with "winning"? I wouldn't say the aggressive party wins a unusually high percentage of wars.
The aggressor may lose, but not until the other side takes the offensive. Staying on defense can buy you time for the enemy to weaken, but if the attacker keeps trying he'll eventually find a way through the defenses. The way to win is to smash the other side, either by occupation or breaking its will. Keeping the offensive also means avoiding the damage from having foreign troops on your own soil. We won the Cold War on the strategic defensive because the Soviet system destroyed itself. There's not many other examples of that working.
It seems pretty wrong to me, it seems like we should all share the sacrifice if there's going to be any sacrifice.
Fighting our enemies has become a privilege reserved for the best of us. I'm not going to be called up to fight unless we get invaded by aliens. There's no way to equally share a task best done by specialists.