If you have rearranged your budget so that 60% of it is provided by one source consistently, then you're not putting the 60% toward new programs, you're using it to finance the existing things everyone already expects of you.

And if you're using that to, say, avoid raising taxes to cover things like inflation or new projects, over time, the level of pain you're going to experience when you either have to make all those adjustments at once or, worse, if the income source is removed, gets worse and worse.

edit: in this case, specifically, it seems like the concern is that even the limited amounts of income from tech companies and knock-on effects from their employees is an enormous lifeline to Ireland's economy, and they're afraid of the rebound effects if it goes away.