3 Nephi 1

After the miraculous signs that occured as prophecied by Samuel the Lamanite -

"...there began to be lyings sent forth among the people, by Satan, to harden their hearts, to the intent that they might not believe in those signs and wonders which they had seen..." (Book of Mormon 3 Nephi 1:22)

And shortly thereafter -

"...the people began to forget those signs and wonders which they had heard, and began to be less and less astonished at a sign or a wonder from heaven, insomuch that they began to be hard in their hearts, and blind in their minds, and began to disbelieve all which they had heard and seen—
2 Imagining up some vain thing in their hearts, that it was wrought by men and by the power of the devil, to lead away and deceive the hearts of the people; and thus did Satan get possession of the hearts of the people again, insomuch that he did blind their eyes and lead them away to believe that the doctrine of Christ was a foolish and a vain thing." (Book of Mormon 3 Nephi 2:1 - 2)

Is it any wonder the Lord explained that -

"...there are those among you who seek signs, and there have been such even from the beginning;
9 But, behold, faith cometh not by signs, but signs follow those that believe.
10 Yea, signs come by faith, not by the will of men, nor as they please, but by the will of God.
11 Yea, signs come by faith, unto mighty works, for without faith no man pleaseth God; and with whom God is angry he is not well pleased; wherefore, unto such he showeth no signs, only in wrath unto their condemnation.
12 Wherefore, I, the Lord, am not pleased with those among you who have sought after signs and wonders for faith, and not for the good of men unto my glory." (Doctrine and Covenants Section 63:8 - 12)

The emphasis being that "signs follow those that believe" not for those to convince them to believe. Moroni wrote that -

"...signs shall follow them that believe—in my name shall they cast out devils; they shall speak with new tongues; they shall take up serpents; and if they drink any deadly thing it shall not hurt them; they shall lay hands on the sick and they shall recover;
25 And whosoever shall believe in my name, doubting nothing, unto him will I confirm all my words, even unto the ends of the earth." (Book of Mormon Mormon 9:24 - 25)

Such signs are reserved for those that believe and will recognize them and not wave them off as "wrought by men". Bruce R. McConkie wrote -

“Gifts of the Spirit which the Lord bestows upon those who believe and obey the gospel of Christ are called signs. That is, their receipt stands as an evidence or sign of the presence of that faith which results from believing the truth. Signs are wonders and miracles; they always and invariably are manifest to and among the faithful saints.. . .)” (Bruce R. McConkie, Mormon Doctrine, p. 713).