Debt is debt, you have to pay up anyway.
I don't care what you plan to use the money for, just pay back what you lend and you will be free, stupid people take loans and spent it on stupid things while the rich and smart people takes loan and use it for a greater course that could benefit them in future.
Still, even if you use loan money to invest in good business there is still a risk, the business might fail and been in good debt or bad debt will be meaningless, because a debt is still a debt.
You are correct that debt must be repaid regardless of the purpose for which it was borrowed. It's important to be responsible with borrowing and to understand the risks involved. While it's true that some people may use loans for frivolous or unnecessary expenses, others may utilize them for investment or other ventures that could potentially yield positive returns.