I used to take numerous steps to prevent my parents from ever accessing IE on their computers. I'd install Chrome or Firefox with adblockers, show them how much nicer the experience was, and leave the Chrome icon on their desktop, start menu, and quick launch panel. But the IE use persisted. So I then hid IE from the Start Menu and changed the default association for all .htm and .html files to Chrome. Still I found they were somehow using IE. To this day, I have no idea how. It occurred to me the other day that they may have been opening the File/Windows Explorer and typing a URL into the folder path, which would then switch it to IE, but I've never been able to confirm.

Fortunately they're both on Windows 10 laptops now, and seem to like Chrome well enough. But even if they somehow trigger one of Microsoft's inane hard-coded associations to open up a webpage in Microsoft's browser, at least it's in Microsoft Edge instead of IE.