and it is free in web, and WP and it was/is free for ARM tablets... so your point?
there is a reason why people choose a phone OS from the other. and I am sure Office it's not a reason. people can give you a lot of names, even the useless crap like "candy crush" and how they can't go WP for that reason but never office was a reason for people to stay or come to WP. (there are many alternatives anyway, free and paid)
The truth is Microsoft with Windows 10 is going to change a lot of things, it will make the ecosystem better in many ways. but it's a work in progress and it can't be done in a day. but Windows 10 will be the key future OS for Microsoft to give phone users a great office version and other apps, and give tablet and hybrid users a touch version.
BUT for example, why would you choose Windows over OSX if you can get office there? even Linux can use office there if they wanted to. there are many reasons why I like Windows over other OSs, and with Windows 10 merging things and making it easier for everyone who have a windows phone and a desktop or laptop or tablet. it would be a huge reason for people to choose MS over other companies.
but like I said, office is not a reason for that, it's just a nice addon we have BUT there are many alternatives available, and Microsoft just want to gain users that lost by those alternatives.
Users see what they want to see, some people think Microsoft is evil so even if Office is free, they won't use it and would use other office apps. so I guess it's just matter of preference for UI, company brand, phone brand, screen size, integration with other devices, etc etc.
to me Windows Phone is nice and amazing, I don't use apps other seem to worry about, and there are 3rd party alternatives for them if I needed some, I am happy with WP. why would other platforms have that I need to switch? apart from fbx viewer and things like that, I see no reason. and fbx in a phone it's not what I would call a need. so I am happy with my choose, and don't go around looking for excuses to switch. I am looking forward what win10 bring and how everything merges, and that's what I am looking for, not "I need today a new excuse to switch platforms". but like I said, it's my preference. if Office it's important to you to the point it was a reason to use WP, then it's ok.