Why is Catholic marriage indissoluble?

Catholics believe marriage is forever because when a man and a women unite in this holy sacrament it's because they chose to be as one. The moment a man leaves his parents he then goes on to join a women in which he is united and through the eyes of God as the Catholics view it, they become one as Adam and Eve did. Also, in Matthew's 5:31 Jesus mentions the question on adultery and divorce in which he states the following "It was also said, Whoever divorces his wife must give her a written notice of divorce, But i tell you, everyone who divorces his wife, except in a case of sexual immorality causes her to commit adultery"

Basically stating that once a married couple who vowed loyalty to each other with the eucharist and in front of witness and especially in front of the lord and decides to break the vow will be committing adultery when he/she becomes involved with someone else, thus breaking the promise.

Also it is mentioned in Matthew 19:3-9

"Some Pharisees approached Him to test Him. The asked, "Is it lawful for a man to divorce his wife on any grounds?"

"haven't you read," he replied, that he who created them in the beginning made them male and female and he also said

for this reason a man will leave his father and mother and be joined to his wife, and the two will become one flesh?

so they are no longer two, but one flesh. Therefore what God has joined together, man must not separate."

"why then" they asked Him, "did moses command us to give divorce papers and to send her away?"

he told them, "Moses permitted you to divorce your wives because of the hardness of your hearts, but it was not like that from the beginning. And i tell you, whoever divorces his wife, except for sexual immortality and marries another, commits adultery."