How come Leonardo Da Vinci leave many of his paintings unfinished?

It could be argued that he left all his paintings unfinished. He himself claimed to have regretted to never having finishing anything. But this was a common thing for artists at the time to claim, because it was like saying, "you think it's a masterpiece, but to me it's not done yet". Michelangelo inscribed Faciebat on La Pieta, which was his arrogant way of saying I could have done better, which is a false humility. In Da Vinci's case, I would say that because he owed so many people money and paintings, it caused a snowball effect in his life that caused him to abandon work so that he could get the money from new commissions, and always playing catch up.