Beyond the choices of what to do with them, word processors also don't really try to educate or nudge users into how to do things. "Typewriter"-type usage, where the user makes all their changes directly as they type or on small selections, is still the dominant pattern of actual user behavior when the system is really built on shared styles geared to allowing you to make document-wide changes all at once.
Ignoring that system makes perfect sense in some cases, but the "magic" that Word and friends use to try to coax some of your input into styles is a constant source of frustration and confusion both for people who do and don't want to bother with styles.
That’s not even the biggest advantage of styles - they have a semantic meaning. Eg headings show up in Word’s navigation pane or auto generated table of contents; or if you convert a word document into an epub using calibre and you used styles correctly then eg each top level heading will be a new chapter.
Ignoring that system makes perfect sense in some cases, but the "magic" that Word and friends use to try to coax some of your input into styles is a constant source of frustration and confusion both for people who do and don't want to bother with styles.