Different sides capture the map at different speeds, e.g. Brits take a while because most of their units only move slowly through neutral/enemy territory and it takes a while for them to get many infantry units since the tommy squads are so costly, while the Axis sides can produce more infantry early on.
Plus, if you're playing against AI, I think they tend to spam pioneers and capture the map really quickly. They also get resource bonuses, so if you are playing AI you are playing a different game than if you play against real people.