Why aren’t there more browsers? Is it just a matter of all the IP tied up by the majors?
For many interested in creating a browser, a new engine is one of the primary reasons for doing so, and so forking or embedding being the only option means that many who would've created a new browser don't, because from their perspective there's no point in a Chrome/Firefox/Safari clone with a slightly different coat of paint.
WebKit at least partially addresses the clone issue, making it easy for developers to write entirely new UI code using their toolkit of choice, but comes with the caveat of not receiving much attention on non-Apple platforms, which is a problem with browser security being so important.