They are much better integrated with the system, their UI is great and they are plain and simple. It's not just Keynote that is good. I used Pages for a lot of private stuff like letters, and Numbers suffices for a lot of simple tables too.
I avoid the MS Office suite wherever I can. Recently went through some lengths to deactive Microsofts intrusive updating background service (nearly as bad in slowing down my system as Adobes).
I would be interested to find out how many individuals and families pay for Microsoft’s software, when apple and google provide free alternatives. (Maybe constrained to families that use mac / iphone, Microsoft might be more popular for Windows families?)
ie: For most people, if you’re not getting free access through work or school, is it actually worth paying for?