To add something to this fact, authors do not include first names for a reason. Nothing is included without intention. In my opinion, he is given no first name because his wife, Mathilde, is the center of attention and is self-centered, and she expects her husband to cater to her fancies for extravagant things, and indeed, he gives up money he had saved in order for her to buy a dress for the ball. Another reason he might not have been given a first name is due to the fact that he was a secondary character, not the primary one, which was Mathilde.
Beyond his last name (Loisel), the husband's name is not given.
His first name is never mentioned in the story. He is referred to as her husband.
"She let herself be married off to a little clerk in the Ministry of Education." (Maupassuant)
"What's the matter with you?" asked her husband, already half undressed." (Maupassaunt