The reason is given in the closing words of Revelation 1:3: For the time is near.
The events described in this book, things that must soon take place,
would happen soon. Though perhaps intimidating and scary, when these things begin to take place, straighten up and raise your heads, because your redemption is drawing near
(Luke 21:28). These words form the theme of the entire book of Revelation. The Christ who ascended is labouring diligently to hasten his return and so inaugurate the fullness of the kingdom of heaven.
3 Blessed is the one who reads aloud the words of this prophecy, and blessed are those who hear, and who keep what is written in it, for the time is near.