Because you’re trying to hire from a small pool of candidates (minority software developer or whatever) that EVERY OTHER tech company is trying to get in a desperate attempt to not look bad (because not having a sufficient number of minorities on staff is a sin).
It’s simply a question of numbers. There’s only so many minorities, and only a fraction of them are sufficiently talented, and everyone wants them. Your company may not be a big enough name to woo these folks. So it’s not necessarily the fault of your leadership to act on their principles.
Now there’s a whole OTHER can of worms associated with DEI, which is that everyone wants minority employees => there’s a lack of them => let’s lower our standards to widen the pool we have to choose from, and your company certainly could go down that route if you think they’re not doing enough.