Much of the data is already accessible from almost any client that can run the BBDL (Bloomberg Data License API, or whatever the name du jour is) Many software vendors embed BBDL pulls using the API. For example, SunGard Front Arena and PolyPaths both pull rates/prices/SMFs/curves seamlessly from BBDL regardless of whether you are running on the terminal or not. This has been the case for over a decade at least.
As for the individual software being available on different machines, they have a solution for some of that (Bloomberg BVAL Pricing Service, or the name du jour).
Ultimately, they want a vertically integrated UX where the models and screens have a very intuitive correlate on their proprietary keyboard (oh, and DRM.) It is a choice, you cant fault them for choosing that route.
There are plenty of competitors who have come along (and died) trying to offer something else. Everyone is free to choose those.
It is a bit like Apple and iOS. I once went to Android for 2yrs, and then came back to iOS because I saw the value of things just working well together.