why was Pilate not interpolated in the cardinal pauline epistles?

[Giuseppe]

Afterall, the simple mention of Pilate would have made easily the point against the Docetists.

Possibly a reason for not interpolate Pilate is the fear of the Roman authorities.

Pilate was mentioned in a forged epistle only in a time when the Christians didn't fear more the Roman authorities and even wanted the martyrdom for propagandistic reasons.

[Giuseppe]

It is even doubtful that Justin mentioned Pilate.

If Justin mentioned Pilate, then it is no surprise that he did so in an apology addressed to the Emperor.