It's easier to start a game by randomly assigning territories, and then putting 3 on each one. 3 stops people from getting 3 dice to attack in every place on their first turn, but is enough to defend with reasonably well. If players had to wait through 20 rounds of deployment while each person put down their initial armies, then a lot more people would stop showing up to play.
That seems reasonable, but I'm curious why they don't have an initial drop system w/ private initial placement (placing all armies at once invisibly) so you wouldn't have to wait 20 turns and still get to plan a custom strategy. The problem with that of course is you end up with everyone fighting over AU,

but I've played some internet games with those drop rules and they work fine.