I am asking for scientific evidence for the claims why they are extinct.
It should be shockingly obvious why they are extinct. They all died. They are extinct for the same reason that wooly mammoths are extinct, they all died. What more of an explanation do you need? We have their fossils. We can compare those fossils to modern hominids. Guess what? None of the modern hominids match the fossil hominids. What more need be said?
You believe they exist however there is no hard scientific evidence they ever existed.
No need for belief. They left fossils for us to study.
The fossil record surely doesn't support it. Scientists have said it themselves.
No, they haven't. Scientists agree that these fossils are transitional. What they debate is the exact placement of these species into the family tree of hominids.
If you disagree that these fossils are transitional then please tell us what features a real transitional would have.
If apes are still alive today then why not the half human-apes?
Because they went extinct. What more need be said? Do you likewise believe that wooly mammoths never existed because they are not alive today?