Because the majority of mankind does not except Jesus as God they don't get the part where he has the athority to forgive men of there sins.
All of them.
Until a you come to believe that Jesus was God come to earth then the bible in it's complete form will not make any sense to you.
The old testament was primarily about mans sin. Mistakes. The New testament is about Gods unconditional forgiveness.
Mar 3:28 VerilyG281 I sayG3004 unto you,G5213 AllG3956 sinsG265 shall be forgivenG863 unto theG3588 sonsG5207 of men,G444 andG2532 blasphemiesG988 wherewith soeverG3745 G302 they shall blaspheme:G987
If you don't believe that Jesus was God then you can not be saved by him because.