Personal opinion: Because Java was all the rage when these people (the programmers) went to college, and so that is what was drilled into them.<p>Many universities, too, are working on out-dated development practices, because the supervising professors either have never worked in Industry, and so are stagnated in terms of tool selection (I'm working on a project right now that still uses SVN), so the students think that that is the correct approach.<p>People are slow to change.<p>Last possibility: perhaps Java is a good choice given the nature (cross-compatibility) and relatively fast speed of the modern JVM.
From what I have seen, many people use the Eclipse IDE and with that Java is the "natural" choice.<p>Agree with @coreyp_1, far too many courses at university focus on Java. Years ago Java was seen as being more "portable" than C or C++ and better able to support OOP - so Java was chosen and taught widely. With all the books and supporting material it is easier to stick with it. Also industry seems to still favour Java. For example, IBM uses Java and Eclipse widely.