No scripture teaches of annihilation and especially none even remotely teach universalism. That is the reason and it is so allowed!
I knew you were going to do that. Okay, let's do three for each:
Annihilation
John 3:15
That whosoever believes in him should not perish but have Eternal Life.
(As it is written, eternal life is the "gift" or "reward" for believing, and it follows that such is not imparted on those who don't believe--aka conditional immortality aka annihilationism--so one has eternal death or non-eternal life when they don't believe)
Romans 2:7
To them who by patient continuance in well doing seek for glory and honor and immortality, eternal life.
(Again, the reward is immortality, so the punishment is mortality, utter destruction, annihilation)
Mathew 10:28
And fear not them which kill the body, but are not able to kill the soul: but rather fear Him which is able to destroy (annihilate) both soul and body in Hell (Hades, or Gehenna, not sure what the original Greek word was).
Universalism
John 6:37
All who the Father has given to Me shall come to ME and him who comes to Me I will in no wise cast out
(If Father-God gives everyone over to Son-God, and everyone with Son-God comes to Him, and He does not cast anyone out, then ALL will be reconciled to God)
John 12:32
And I, if I be lifted up from the Earth, will draw all men unto Me.
(This one works well with universalism and Hell being in the presence of God, but how can men be drawn to Him, and also separated eternally? Perhaps for the final judgment, but in that case, why not just say "...will judge all men" why say draw, which indicates a universal reconciliation?)
1 Timothy 2:4-6
(God) will have all men to be saved and to come unto the knowledge of the Truth. For there is one God, and one Mediator between God and men, the Man Christ Jesus. Who gave himself a ransom for all to be testified in due time.
(Fairly straightforward this one is, God wills something, He is omnipotent, so it will happen)
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I do not necessarily endorse these opinions, but I have been forced to play devil's advocate.
Also, how do you solve the loving God paradox? That is why would a Loving God allow anyone to be damned to Hell if there was a capacity to have them saved? And I don't mean really wicked people, let's say a moral atheist who just isn't convinced of the evidence, but who would follow Christ if the evidence were made clear?
Also I want an apology for your post, because if you look at just these scriptures, they teach either annihilation or universal salvation, which is what on-the-face-of-it means. (Though I think Hell would freeze over before that happens, and in that case none of this matters)