To flesh this out a little more: The question should be "Why isn't Java used by startups or for small projects?". Java certainly used for "modern Web apps" at

To flesh this out a little more: The question should be "Why isn't Java used by startups or for small projects?". Java certainly used for "modern Web apps" at more established companies. The issue is one of speed vs scale. Startups need to get to minimum viable product. They are usually small teams of 1-3 engineers, and value iteration speed over performance or maintainability. Running up against scalability issues or team code code maintenance issues is a problem "you'd like to have", that is, by the time you reach that stage, it's a sign your initial implementation helped you over the initial hump of getting customers or investment. You can afford to rewrite the app at that point. A company like Google can afford the luxury of building things for scale up front, even though they may be wasting their time implementing scaling for something that might get no users, because they can absorb the loss. At least, that's my opinion, that many many "cool", "hip", "modern" companies build small apps with small teams where iteration speed and simplicity are the greatest requirements.