Actually, ever since introduction of the Ribbon in Office 2007 I found the styles to be much more prominent than the presentational formatting. Not that it stops anyone who doesn't want to learn how to use Word properly to still use the latter, but simply by size and visual importance in the UI styles are far more into your face than the other formatting options.
And sure, it takes some discipline to use styles, but that goes for any other option as well (apart from things like Docbook maybe). You're supposed to use \em in LaTeX instead of \textit for the same reasons you're supposed to use an Emphasis style in Word instead of italic text. The only difference is that the mechanism is the same in LaTeX (type a few characters – which is pretty much why for any given macro you'd be hard-pressed to actually decide whether it's semantic or presentational), while in Word it's a separate feature.
And sure, it takes some discipline to use styles, but that goes for any other option as well (apart from things like Docbook maybe). You're supposed to use \em in LaTeX instead of \textit for the same reasons you're supposed to use an Emphasis style in Word instead of italic text. The only difference is that the mechanism is the same in LaTeX (type a few characters – which is pretty much why for any given macro you'd be hard-pressed to actually decide whether it's semantic or presentational), while in Word it's a separate feature.