Reduced scale of gameplay

[Malorn]

Footholds don't prevent domination of a continent. They do give better accessibility and allow you to more easily mount a reasonable offensive.

If PS1 taught us anything it is that the masses typically move to the next nearest objective along the path of least resistance (typically a road).

In PS2 terms that means people will fight out from footholds, and if there isn't a foothold you won't see any serious offensives there.