Once you have a bunch of important documents locked up in Office file formats -- which Office is the only app guaranteed to be able to read reliably -- you have a great incentive down the road to start sending money to Microsoft so you can continue to access them.
Subscriptions bleed money from users continually, regardless of how often they use something. Paying for major upgrades only allows the user to upgrade based on whether they need certain features and potentially skip every other update or so if they use the software only lightly.
For example, my personal at-home copy of MS Office is the 2003 version. I use it so rarely that this does not matter, especially with other options available that can view and edit MS Office documents.
I stopped using VMWare Fusion, for example, because they got into the habit of releasing paid upgrade versions that were required in order to run on Apple's new OS X version. Perhaps it's not their fault that Apple's OS updates broke VMWare's virutalization, but I don't use this often enough at home to want to pay for an upgrade every year. Before I would pay for an upgrade every 2 or 3 years. Now I've switched to VirtualBox at home.
For business use, software is used much more often and it matters a lot more to have it up-to-date. So in that case a yearly subscription might make sense.
Maybe a few years ago. I'm not sure how many CIOs are still drinking that Kool-Aid today, though.
If you really use Office every day during the workday, it's worth the money. The $15/m that my company pays per user for our 365 account is well worth the money.
I don't understand why that was downvoted. Office 365 is expensive...compared to a one-time purchase you own forever. I don't understand why users aren't showing more resistance to subscription-based software (Microsoft, Adobe, etc.)...it's as if people enjoy getting screwed over.