To each his sufferings: all are men

Condemned alike to groan

The tender for another's pain

The unfeeling for his own.

Yet, ah! why should they know their fate

Since sorrow never comes too late

And happiness too swiftly flies?

Thought would destroy their Paradise.

No more—where ignorance is bliss

'Tis folly to be wise.

-Thomas Gray

I can't think of an example where ignorance would impede the ability to use ZKPs. That could just be because I haven't thought it through enough  (or am too ignorant), so if you (or anyone else) can think of an example that would be great.

Interesting question.