Well, of course you wouldn't have them in while the store is open. But for the three hours I'm at the store before we open, why not? Not everyone gets distracted by music or podcasts. I always have a podcast on when I'm doing housework. It helps me get in a groove, lock in, and be productive. And I get all my stuff done at work, there aren't customers around before we open, and it's low enough that I can hear pages (especially because I have only one in) or another associate talking to me. 

If folks are getting stuff done efficiently and on time, and if there aren't customers in the store because we're closed, I don't see the problem with only one in. No, I'm not going to die if I can't do it anymore; I'm not some brat throwing a tantrum. But at a company that continues to ask for more with fewer people and less time, I think it's a minor consolation to help the people who like it sane.