Some bibles don't have any Mark 16:9-20 in them because the earliest manuscripts don't include them. Why do you believe they should be included?
It really makes no difference to the message of the Bible whether Mark 16:16 needs to be included or not because the truth of Mark 16:16 is the same throughout the New Testament. Jesus commanded baptism in His last words to His disciples in Matt 28 :18-19 just before His ascension into heaven. Mark describes a similar scene in His account also just before Jesus’s ascension. Jesus taught Belief and baptism and the conversions in the rest of the New Testament act out that teaching. Read these scriptures.:
Acts 2:38- those Jews already believed when they asked Peter “What must we do?” Peter didn’t tell them to BELIEVE because they already did but he did tell them to repent AND BE BAPTIZED for the remission if sins. So what did those Jews in Acts 2 do? They BELIEVED and were BAPTIZED.
Acts 8- the Samaritans, verse 12 - BELIEVED the things Phillip preached and both men and women were BAPTIZED.
Acts 8:13- Simon the Sorcerer, BELIEVED and was BAPTIZED.
Acts 8:36-38- the eunuch said, “ I BELIEVE that Jesus Christ is the Son of God.” And Phillip BAPTIZED him.
Acts 9- Saul of Tarsus- BELIEVED AND IN Acts 22:19 washed away his sins in BAPTISM.
Acts 16: Lydia, BELIEVED (verse 14) and was BAPTIZED ( verse 15).
Acts 16:32- the jailer and his house BELIEVED in verse 32 and were BAPTIZED in verse 33.
Acts 18:8- “And many of the Corinthians hearing, BELIEVED AND WERE BAPTIZED.”
So, you see, even if Mark 16:16 were not in the Bible at all, would make no difference to what is TRUTH or to what the Bible teaches or to proving that you must believe and be baptized to be saved. The SAME THING is taught in at least 8 other scriptures. And I haven’t even mentioned Hebrews 11:6 that says without faith it is impossible to please God or 1 Peter 3:21 that proves that baptism saves us. Faith and baptism are taught all over the New Testament—it’s just that like Psalms 119:160 says, you must take the SUM of what God says and put it all together to get the “TRUTH.” God’s truth does not depend on one passage of scripture.
I happen to believe that God is fully capable of preserving and PROTECTING His word, the Bible. I have faith in God enough to believe that if Mark 16:16 did not need to be included in His word, He would and COULD make sure it was not there. Thus, I believe it is perfectly valid and is there by His divine will.
My faith is simple. I just believe God is able and HAS provided us a book that we can trust. He would not allow us to be led astray by HIS book. I feel that I can teach Mark 16:16 with full confidence that it is indeed the truth.