The fact that you haven't had it enabled for years is probably why you can't understand its usefulness. It's just not part of your workflow because its not available. It does in fact provide a lot of value. As an example, entering uppercase alphanumeric codes is annoying without capslock (switching from holding shift for uppercase letters to remembering to let go of shift to enter a number really slows down entry).
That's not really an example of why something in all caps is useful, though.
The only time I've seen anyone using caps lock is in a call center where people think it's the proper way of entering data into a form (my opinion is it's totally not).
