Why not gnat Ada in gcc?

[Richard Kenner]

    > have wondered why the gnu crew would not have decided to add Ada to
    > the already substantial capabilities of GCC

    AFAIK, it's because part of GNAT is written in Ada, so you'd need an
    Ada compiler to bootstrap it, and few people have one handy.

That's half the reason.  The other half is that it's a *lot* of large
files and there's still the question of whether it makes sense to put
it into the main repository.