[sdunwoody]

Using a custom library over Bootstrap would potentially offer them the following benefits:

* Full control over browser support (Government Agencies are likely to have to support older browser than Bootstrap for example would support).

* Full control over accessibility (as far as I know, Bootstrap is not entirely accessible).

* Ability to limit customisation to more closely fit any government style guide etc.

* Not needing to update the version they are using whenever Twitter drop support for older versions, as they completely control the development life cycle and how long they support each version for.

Possibly some other ones I have missed as well.

Would they have saved money in the long term by using Bootstrap? Quite possibly (although I think it is hard to say definitively, and I really doubt creating this library cost significant amounts of money).

Would using Bootstrap have resulted in sites that didn't look as nice? I highly suspect so.