I think what a lot of people tend to forget is that WordPress websites are not only used by individual bloggers.
There are plenty of people, myself included, who build websites for others, mostly companies.
Now with that in mind, what do you think I do with these rotten widgets? You think I (want to) show them to my clients?
Of course I already fully customize the dashboard for my clients, but all those widgets just bring additional work that is completely unnecessary to begin with!

And as we're on the topic of adding crap to the dashboard, you might as well also touch on the mess plugin developers are starting to make of the Toolbar!

For both the widgets and the toolbar menus we need as an absolute bare minimum the choice of turning them OFF. Better even would be off by default and the choice of turning them on. Ideal scenario would be not there to begin with.