In many applications (JIRA, Vim) typing without being in a text input field can cause all kinds of trouble. Heck, in browsers if you type 'backspace' you can end up going back and page and blowing away all of your precious form input. Not to mention the very real possibility that their work, the text they've typed, will be dropped on the floor. We have been trained by these dangers to avoid typing without a text prompt.
This is why Google switched the 'Back' function to Alt+Left Arrow in Chrome. You could be trying to delete something out of a web form and accidentally leave the page.
That's when I switched to Firefox. I've been using the backspace key to go to the previous page or directory since the mid-90's and I never accidently left a page when trying to delete stuff.
