Being in the legal field, I need to transfer documents and be sure they are formatted correctly. LibreOffice is maybe 90% as easy as Word at creating documents, but editing and saving Word files it frequently messes up something. Sometimes it's minor and sometimes it's not, but I'm not going to spend 11⅑% more effort making documents in addition to taking that chance just to avoid Microsoft.

In addition, there's nothing close to Outlook. Thunderbird works okay, but it's definitely not an acceptable replacement. I'd sooner use Outlook's webmail.