Why was a man excluded from heaven for lack of a wedding garment?

In Jesus' parable in Matthew 22, why was a man excluded from heaven for lack of a wedding garment?
11 “But when the king came in to see the guests, he saw a man there who did not have on a wedding garment. 12 So he said to him, ‘Friend, how did you come in here without a wedding garment?’ And he was speechless. 13 Then the king said to the servants, ‘Bind him hand and foot, take him away, and cast him into outer darkness; there will be weeping and gnashing of teeth.’
Answer:
The key to understanding this parable is identifying what the garment represents.
The wedding garment is the same as the robe of Christ's Righteousness. It is what we are given when we consecrated our lives to the Lord. It covers our sins and gives us a standing with the Lord.
Isa_61:10 I will greatly rejoice in the LORD, my soul shall be joyful in my God; for he hath clothed me with the garments of salvation, he hath covered me with the robe of righteousness, as a bridegroom decketh himself with ornaments, and as a bride adorneth herself with her jewels.
Rev 7:14 And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.
If we do not have it on, we stand in our own filthy rags.
Isa_64:6 But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.
We are also told about those who come in through another way being a thief and a robber.
Joh_10:1 Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber.
So if this person came in another way, and not by Christ--he was not invited and crashed the wedding.
11 “But when the king came in to see the guests, he saw a man there who did not have on a wedding garment. 12 So he said to him, ‘Friend, how did you come in here without a wedding garment?’ And he was speechless. 13 Then the king said to the servants, ‘Bind him hand and foot, take him away, and cast him into outer darkness; there will be weeping and gnashing of teeth.’
Answer:
The key to understanding this parable is identifying what the garment represents.
The wedding garment is the same as the robe of Christ's Righteousness. It is what we are given when we consecrated our lives to the Lord. It covers our sins and gives us a standing with the Lord.
Isa_61:10 I will greatly rejoice in the LORD, my soul shall be joyful in my God; for he hath clothed me with the garments of salvation, he hath covered me with the robe of righteousness, as a bridegroom decketh himself with ornaments, and as a bride adorneth herself with her jewels.
Rev 7:14 And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.
If we do not have it on, we stand in our own filthy rags.
Isa_64:6 But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.
We are also told about those who come in through another way being a thief and a robber.
Joh_10:1 Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber.
So if this person came in another way, and not by Christ--he was not invited and crashed the wedding.