I think it is plain from the story, as our Lord told it, that this man might have had a wedding garment if he had chosen to do so.
Doubtless the servants had beautiful clean garments ready in another room, which the King had provided for every guest to put on.
But this one guest had no wedding garment!
Then the King said to him: "Friend, how did you come in to the banquet without having a wedding garment?"
But the man was speechless; he had no answer to make; he had no excuse to offer. Perhaps he thought his own clothes were good enough for any wedding feast! Perhaps he had been angry with the servants for offering him the King's garment!
We are not told—we only know that unless he had that garment which had been provided, he could not taste of the King's feast.
The King ordered him to be sent away; and, in the dark night outside, how earnestly he must have wished that he had not been so proud, or so careless; and how he must have wept when he realized all he had missed.
I think that the Lord Jesus told this story as a solemn warning against some things which prevent people from entering the "Kingdom of Heaven."
These things are just as likely to prevent people now, as they were in the time that our Lord gave this parable to the multitude.
The chief danger is carelessness.