Exactly.
When you're in a pitchers duel, and you get Crawford or Ells on 1st, that's turned into a double, potentially even a triple. They can swipe 2nd, or hell, Ellsbury tagged up from 1st on a deep fly ball last night. And it doesn't take a ringing single to get them on 1st. Crawford had 2 infield hits last night. Stole 2nd on 1, stole 3rd on the other after being moved on a ground ball. I mean honestly, there's very little difference between an infield hit and a SB vs a Double.
They have the ability to completely change the game with their legs. If anything, we're going to see the significance even more in low scoring games, not slug fests.