That's a good point. There can still be small maps that are good strategy maps.
The problem is with the maps that some players choose to post dozens of times in a row to eke out victories by employing the same tried-and-true tactic repeatedly: race to one city at a chokepoint and you've won.
That's not strategy, and it's not much of a game. Those wins should not gain the player many (or any) ladder points. I'd suggest excluding certain maps, but it might be more fair to scale the points awarded by the number of turns needed to win. That solution comes with its own drawbacks, so it's not my first choice.
Even more important is the issue of separating out newbies from the ladder.
How many players do you think have been turned off to the game after playing one of those matches, on a map with 10 cities, with a player who is basically trolling for ladder points? If that's the first game you join upon entering Warbarons, it will probably be the last one you ever play here.