Yeah, it makes life more difficult for developers. Just like the variety of linux distributions. And yet I don't hear anyone here whining about how we need to all standardize on Oracle Linux.
You don't hear that whining much anymore because of a few reasons.
1) many people who valued standardization of experience moved to other platforms
2) on desktop systems, you can fairly straightforwardly (though not always easily) compile from sources to get an executable binary compatible with you hardware. With mobile/tablets, that's rarely the case (i'd say never, but I don't know about edge case devices out there which may support/encourage it).
I think it's more accurate to say that the linux community engineered around it. Think about the package distribution systems that have evolved: apt, yum, slackpkg, etc. Installing software on a linux distro is WAY easier than than installing software on my Mac. Compare running aptitude install MySQL to going to the MySQL website, downloading a dmg, and running an installer.
This kind of package management would never have evolved under the One True Dogma of Sun or Oracle. Windows still doesn't have it. Apple has finally put an App Store on OSX, but of course with their usual dictatorial flair.
Java is a dying community. This is 100% Sun's fault. The only flourishing parts of the Java ecosystem (Android and App Engine) are flourishing because they dared to speak heresy.
