The issue is the perpetual ownership.
If I lend you money, you only own me the money I've lended+interest. I'm not going to have a stake on your future businesses, nor have any decision power over you, it isn't in my power to make sure you squeeze the most money possible over your job. You pay the money back and we are done.
Even then you can just add a higher interest rate. You absolutely don't need to held the company hostage until the heat death of the universe.