I'd love to be able to connect an adapter to my tools when I'm in the shop rather than have to always run them as cordless. I've invested a lot of money in tools with batteries, and it drives me nuts to have to swap out batteries every few hours in the shop. I have 110v outlets all around the shop, and I'd LOVE to be able to take advantage of them while I'm in the shop, then take the same tools with batteries on the road with me when needed. It would reduce wear and tear on the batteries. By reducing the wear and tear, it would also reduce the number of batteries that have to enter the waste stream each year when they won't take a charge any longer. (Yeah, I know that's a stretch!)
Historically, my corded tools were more powerful than my battery operated tools, but the newer brushless tools are giving corded tools a run for their money power wise.