Specsavers ad on the radio is saying, "We could all do with a spare pair." That is, of course, if you can afford it. Prescription glasses cost about $700. Can you afford to have a spare $700 just sitting around doing nothing?

But what do you want with a spare pair? When would you wear them? And why? What's wrong with the pair you are wearing? Particularly if you only take them off when you go to bed. And you don't need a spare pair then.

So why ". . . could we all do with a spare pair."? I just don't understand it.