I don't think it has to do with familiarity at all - LibreOffice looks almost identical to what MS Office looked like prior to Office 2007, so it's definitely f

I don't think it has to do with familiarity at all - LibreOffice looks almost identical to what MS Office looked like prior to Office 2007, so it's definitely familiar, and if you look at 'percent of my life using a UI,' is even more familiar. When the Ribbon was introduced, everyone complained because it was different, but I thought it was a great innovation. Common tasks that used to be buried in menus were brought to the forefront, and really useful actions that few people knew about got exposed so that you didn't need to be a power user to access them. Microsoft invested a lot of time to figure out how people actually used the software and streamline it for them, and it shows in the product. As a quick example, look at what it takes to change a spreadsheet to print in landscape and fit to a page in Calc vs. Excel. It's a pretty common task for anyone who prints out a spreadsheet, so Excel made it easy. Calc still does it the same way Excel did ten years ago, based on where a programmer would put those options, but not where a user would look for them.