This would work if there are no other currency which can used for payments. So long you can use Fiat or Paypal or whatever, Bitcoin will not be a Payment currency, which got hold by millions of people worldwide for shopping somewhere quickly.
Another option, if you could buy things ONLY with Bitcoin, this could increase the worth too.
Well your right about that people don't need to hold bitcoin to shop online, because they have alternatives like Paypal, however since bitcoin cuts transaction fees by 90 % or so , because they cut out the middle man, online shops selling stuff in bitcoin can offer lower prices then shops that use paypal for example. so this could lead to the situation where you can get stuff online cheaper when you use bitcoin.