They don't have to be, but in the absence of evidence, they are. That's just true by the definitions of the words.
Put another way: not all faith is blind, but faith without skepticism is blind faith; not all confidence is unjustified, but in the confidence without justification (evidence) is unjustified.
Put another way: not all faith is blind, but faith without skepticism is blind faith; not all confidence is unjustified, but in the confidence without justification (evidence) is unjustified.