Why don't today's Christians "believe on Jesus" (Jn 6:47) so they can have their proof atheist & unbelievers are asking for?

It doesn't matter what atheists are asking for. They are not the ones who determine what we believe and do!

There is already plenty of proof to convince atheists, if they will receive it with an open mind and examine the evidence.  If they still do not believe, they are "without excuse" ! (Romans 1:19-20)

The scriptures are sufficient to convince a person with an honest and open mind to believe.  That is why they were written! (John 20:30-31)

If they will not hear the scriptures, "neither will they be convinced if (they saw) someone... rise from the dead.’” (Luke 16:31)

The miracles happened just as Jesus promised for the divine purpose for which they were intended. (Mark 16:20)

Some who saw them said, "indeed, that a notable miracle has been done through them is evident to all who dwell in Jerusalem, and we cannot deny it." ( Acts 4:16). They, however, still disbelieved

Atheist ask for signs, but they do not believe the word of God that has already been confirmed by signs!  Once something is confirmed, there is no need to confirm it again!

The purpose of miracles has been accomplished.  The scriptures say once this was done, those miracles would cease!

I believe in Jesus and rely on Him.

I see you took a break from deal doughing yourself to deal dough others again .

Christians couldn't care less about Jesus, nor do they have any interest in evangelizing.

Your question is based on assumptions that are 30 years out of date. Christians have a new messiah now, and a new mission.