Mormon 7:7 And he hath brought to pass the redemption of the world, whereby he that is found guiltless before him at the judgment day hath it given unto him to dwell in the presence of God in his kingdom, to sing ceaseless praises with the choirs above, unto the Father, and unto the Son, and unto the Holy Ghost, which are one God, in a state of happiness which hath no end.
D&C 76:50, 62, 70-71, 77, 81, 85-86
50 And again we bear recordâ€”for we saw and heard, and this is the testimony of the gospel of Christ concerning them who shall come forth in the resurrection of the justâ€”
62 These shall dwell in the presence of God and his Christ forever and ever.
70 These are they whose bodies are celestial, whose glory is that of the sun, even the glory of God, the highest of all, whose glory the sun of the firmament is written of as being typical.
71 And again, we saw the terrestrial world, and behold and lo, these are they who are of the terrestrial, whose glory differs from that of the church of the Firstborn who have received the fulness of the Father, even as that of the moon differs from the sun in the firmament.
77 These are they who receive of the presence of the Son, but not of the fulness of the Father.
81 And again, we saw the glory of the telestial, which glory is that of the lesser, even as the glory of the stars differs from that of the glory of the moon in the firmament.
85 These are they who shall not be redeemed from the devil until the last resurrection, until the Lord, even Christ the Lamb, shall have finished his work.
86 These are they who receive not of his fulness in the eternal world, but of the Holy Spirit through the ministration of the terrestrial;
6 Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.
7 If ye had known me, ye should have known my Father also: and from henceforth ye know him, and have seen him.
8 Philip saith unto him, Lord, shew us the Father, and it sufficeth us.
9 Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Shew us the Father?
If the Father, Son, and Holy Ghost are one God, and he that sees and knows the Son sees and knows the Father, what is the practical consequence of those in the terrestrial kingdom having the presence of the Son, but not the fulness of the Father, and those in the telestial kingdom having the fulness of the Holy Spirit, but not of the Son or the Father? Why is that an important point?