Android Market makes it easier to install apps with just one click but lacks QR codes. But why would someone need QR code when he/she can simply sign in and push the apps directly to the device? It is an interesting question but I can see various scenarios where a QR code would definitely come useful.
Suppose a group of friends browsing around the Android Market. Not everyone can sign in to push the apps to their devices. Therefore, the best case scenario for everyone would be to use Google Goggles or Barcode Scanner to download apps directly to their devices. Now suppose another situation where writers (like us) and users (who post on forums) want others to try out an app, we can simply post the QR code making it easier for them to download. Showing a QR code on the app page also means that you can print them too.
Droid Code is a nifty extension for Google Chrome that generates and displays QR codes on-the-fly for every Android app in the Android Market. It requires zero configuration and has no other purpose. We downloaded some apps without any issues using QR codes generated by this extension. It works surprisingly well.
Unless Google does not add QR codes by default, users have no choice but to use Droid Code extension. It is a great example of doing one thing well.