Not being repaid is possibly a reason not to lend him any more money. I don't see it as a reason to cut contact with him, though.
My motto, is that people have helped me a lot in life, with time, resources and sometimes money.
If I loan money, I explicitly do not expect to be repaid, and will generally say, pass it on.
Also it's often not the loaner side who cuts off contact. But if the person who receives the loan cannot repay it, and every time they talk to you, they feel guilty and think about it. They might just start avoiding you.
The moral dilemma might be more significant if the amount is large enough to worry you.
Suppose a close friend needs $50k for medical treatment, but it's $50k you had saved to pay for your child's university, and they promise to pay you back gradually so it's in time for your child to start university, but meanwhile they don't pay any back, and instead spend their income on a fancy car. I think it would be challenging to remain friends with that person.
Thus, if you read this comment, you owe me $5, payable via nothing, because money is a construct anyway. So if you can afford to, give your friend a monetary gift. If they can't repay you, and you can't afford to not have that money, then you can't afford to lend them that money and you have to learn to say no.