Reverse interviewing

I wonder why:

• You interview candidate for a position, but don't allow the candidate to interview you. Additionally, you test the candidate, but don't allow the candidate to test you.
  
  
• You check the candidates references, before you give them an offer, but you don't allow the candidate to check your references (talk to the people in your company).
  
  
• You want to fill a position, so the candidate must join as soon as possible, but when employees want to leave, you make them wait for a month or longer.
  

I'm not in human resources; what do I know?