[JPLeRouzic]

There are several possible reasons, but it may be because the strategic goals changed since WWI and WWII.

Those two worldwide wars were quasi-colonial wars. Powers of the time were competing to become as powerful economically and militarily as possible.

However, the war didn't end with WWII, since at any time there were around 20/30 wars in a quickly changing landscape. It's just that were not done in the Western world (except in the Balkans in the 1990').

Since that time there have been mostly two types of military conflicts by regional actors:

* Low-intensity conflicts (the multiple "liberation" armies, religious wars or warlords as in central Africa)

* Conflict between main powers via proxy.