Every store should have a website. Not just any website, but a website where you can shop and make PURCHASES. I'm surprised that so many stores still don't. A website is an extension of your store and a great way to communicate your brand. By not having a website with online purchasing you are doing consumers a disservice. A few stores I would like to see with online shopping: H&M, Express and The Limited (doesn't even have an actual website). I understand this is much harder for smaller boutiques that don't have the resources but it's becoming easier (therefore cheaper) to setup a site yourself.
More and more people are shopping and buying online. Everyone is busier these days so online shopping makes it easier for those that do not have time to go store to store. Without a website you might be missing out on a whole other audience. It also can drive offline sales - many people research online before buying in the store.