Why some human resources specialists advise applicants to wait for the result of the interview even if obviously the applicant is not qualified?

I agree with you. Interview board always respect to candidate as their valuable knowledge, skills and behavior. Without assessment of all candidates, interview board does not say you are selected or we call you for that reasons they said wait for getting result. Job seekers are eager to know the result for that reasons HR needs to inform interviewee whether they selected or not.         

untill end of the interviews of all candidate .. the interviewer never open to say someone is sleceted or rejected . may the the first candidate perfect for the job but the2nd one is more than perfect... so at end of all interviews thay judged that which candidate will be more suitable for this job .. 

i think the interviewer don't say if someone accepted or not because if that person got a personal talent he would know if he accepted or not :D

This is due to urgency of the vacant opportunity........... by the way the pplicant can judge himself better.