The book of I Peter was written to Christians that were experiencing great persecution and suffering.
They were sailing in uncharted waters with danger lurking on every side as they tried to live for Jesus. Their questions in the midst of their suffering were the same as ours. Where is God in all of this? Why are bad things happening to such good people? Why does evil seem to go unpunished, while the good seem to only have trials? Peter was well aware that those that were reading his letter were living out those questions every day.
Peter wrote to a group of Christians that had been scattered away from their homeland. They were living in a foreign land and being attacked by an enemy. In I Peter, he addresses the whole church as aliens, strangers, outsiders living in a foreign land, facing an enemy that wanted to destroy them. He reminded his readers that this world was not their home. He gives them counsel and comfort by reminding them of their living hope in the Lord, and by assuring them that their reward and treasure is laid up for them in a place where it would never fade away.
The message of I Peter never stops being relevant because trials and struggle come to every person.