My guess is, it's more than just technology.
These days all companies are focusing on a smaller core set of services to
save money and it may very well be that they have decided not to support
java for business reasons. (And thus choosen a quite ... ungraceful
explanation...)
A quick swoop of their site seems to indicate they are mainly focusing on
java-applets. I am not so familiar with java-applets but i have worked with
html and dhtml before and i've had reason to curse different browsers way
of interpreting things many times. I am guessing that they may have seen
incompatibilities in the implementation of java in different browsers and
decided it is too much work to coordinate. But this is just a guess.
Here I'd like to add, in my world java is mainly a server side language for
web application development, so i have no reason to fear or even get too
invloved with any lacks in the implementation of applets... maybe this
changes one day and i realise some kind of problem but so far java works
well for me.
I am too ignorant on the security angle to give any input on that.