Most villages also give something other than just Actions. Even that +1 card means if you didn't have a smithy in my hand, I could still pick it up. I can have metropolis every hand, but I still need Smithy in my hand. If I don't, then it's a completely dead card in my hand. I can maybe see this at $4 maximum.
Think of it like this. If I keep topdecking it, I draw less cards from my smithys, since I don't actually get anything from Metropolis. If I don't get another Smithy in the 2 cards after the topdecked Metropolis, then I'm stuck. Regular Village doesn't have this problem, since it replaces itself in your hand. I get Village, play it, draw a card and still have a 5 card hand. And even those that lower your hand size like Fishing Village give me something like $. This lowers my hand size and limits what I can draw. Sure you'll need one village in your deck, but you'll need way more +cards.