The baby swing

I think the baby swing is quite possibly the best invention EVER! But, riddle me this: WTH don't they make them with a plug? Must EVERYTHING run on batteries? Duracell must know how much my babies like the swing and I'm singlehandedly bailing them out with my battery purchases....must find that battery charger and rechargeable batteries I bought for the swing when Madison was a baby, but we've moved since then...hmmmm