Why is the bowl-judgment prophecy written?
The bowl-judgment prophecy is written as a warning and an instigation for unsaved people to get right with the Lord, since these final plagues complete God's wrath and are awful. Believers are not appointed to this wrath; the church is insulated and taken out before these judgments.
Les explains that Revelation 15 introduces the seven last plagues, the bowl judgments, which are the final, consummated wrath of God. These judgments intensify and come faster as the tribulation winds down. He notes this period is not a time of love, mercy, and grace but of God's wrath. For believers, the church is insulated and will be taken out before these things, because Paul makes plain we are saved from wrath, not to it. For those who never experienced salvation, the prophecy is written as an instigation and warning to get right with the Lord, because the physical suffering and pain will be awful and without hope of escape.