If you are lending some money to a friend or a person, you don't care what they do with it and what they bet on, as long as they have a way to pay it back.
Lending money and funding gamblers are two separate things and should not be mixed with each other.
When you lend money to someone (gambler), you do not care what he will be doing with that money. You are only concerned that he pays you back on time and secondly, you know that you will get more or less the same amount of money. Even if he doubles the money through gambling, it is none of your concern.
Funding a gambler means that you are giving money to the gambler to gamble with it and most probably you will share the profit with him, meaning if he doubles the money, you will get 50% of that money (or whatever the percentage amount is agreed on) plus you will also get the seed money back. The problem here is that people forget to document what will happen if the money is lost in gambling and will the borrower share the loss too?