[baq]

All those apps are Office in the limit; it’s just that some won’t make it. People want their office suite integrated into one Swiss Army knife in the hopes of a better experience than a dozen specialized tools which only marginally cooperate.

[Ekaros]

And also for organisations single tool is likely to be cheaper collecting number of separate ones, each with their own subscriptions and over head in managing that.

Which really is what makes MS offering so good.