Although it is fallacious to appeal to one's reasons for believing in a doctrine to criticise the doctrine, there is clear motivation for belief in Annihilationism. It is so much nicer than the doctrine of Hell. But Annihilationists dispute this. Is Annihilationism really nicer than an eternal Hell? After all, eternal suffering may well be awful, but is it really as bad as just not existing?
The answer seems obvious. We're not just talking about having the sniffles here. We can suffer on the earth and still be glad we're alive (of course, made easier by the possibility of healing). But in Hell, we're talking about an everlasting lake of fire from which there is no escape, and no relief. Such a fate is so intolerable, unbelievers criticise Christians for believing it, let alone daring to preach it.
Notice, Annihilationists don't tend to receive such criticisms. Imagine, an atheist walks up to an Annihilationist "hey, what happens to me in your religion if I don't accept it and I'm wrong?" "Uh... pretty much the same as if you're right." They're already Annihilationists! It's not just a nicer doctrine, it's what they already believe, and will aggressively defend if you try to take it away from them.
It would seem obvious, then, that the whole reason Annihilationism was made up is precisely because it is nicer than eternal damnation. It doesn't draw the same criticisms as eternal Hell, the main argument for it is that it doesn't seem as cruel as an eternal Hell (and thus doesn't put as many unbelievers off Christianity), it's quite clearly a more tolerable belief than eternal Hell.
So we clearly have motive here. The ironic thing is, it doesn't matter. The question isn't "which view is nicer", but "which view is true". If Annihilationism was true, I'd want to jump right on that train. After all, I have two grandparents who died without Christ. I would love to believe they will just rot in the ground until the elements melt in the fervent heat. But if it's false, it doesn't matter that it's more tolerable. Why should we expect God to capitulate to our sinful desires? His judgments are greater than ours. "“For My thoughts are not your thoughts, and your ways are not My ways.” This is the Lord’s declaration. “For as heaven is higher than earth, so My ways are higher than your ways, and My thoughts than your thoughts." (Isaiah 55:8-9). Let us therefore say with the Psalmist "You are righteous, Lord, and Your judgments are just."