Why was Revelation Written Using Symbols?

Somehow somewhere at one point I heard that John wrote Revelation using cryptic symbols in order to avoid detection and persecution by the Roman empire. I was led to believe -- I don't know by whom -- that given the persecution Christian community then was facing, John had to make his message difficult to decipher; and only the faithful could read it and decipher, the rest would get lost with all the symbols and the numbers. I was mistaken.

As Jesus finished speaking to the people about the parable of the sower (Matt 13), his disciples came to ask, " why do you speak to the crowd in parables?" Jesus replied, " The knowledge of the secrets of the kingdom of heaven is given to you all, but not to them". Then he went on to say, drawing from the book of Isaiah, that he spoke in parables because:

"Though seeing, they do not see;

though hearing, they do not hear or understand..."

"But blessed are your eyes because they see, and your ears because they hear."

"He who has ears, let him hear."

This is to mean that Jesus used parables to draw the attention of the listening believers, while leaving the unbelieving listeners clueless as to what he was saying with the parables.

John also used the phrase " he who has ears, let him hear", drawing from Jesus and from the Old Testament writers like Isaiah and Ezekiel. So just as Jesus' use of parable was to obscure the message from the unbelieving listeners, but open up a very vivid dimension of the message for the believing listeners, John used symbols and numbers to "open the eyes of true believers while leaving the hardened unbelievers in deeper darkness" (Beale & Campbell. Revelation: A Shorter Commentary. 2015. p. 16).

So the cryptic symbols in Revelation is not to obscure the message to the readers, but to obscure the message for the hardened heart. The Pharisees listened to the parables of Jesus one after another, yet most of them failed to KNOW Jesus though they understood the parable in certain sense and plotted to kill Jesus. As parables were to Jesus in his communication -- vivid, clear, contextual; symbols were to John in his communication.