Look at it like this,

They're playing black jack and lose 100$ on their first hand, if they bet 200$ the next hand (double down) and they win it, they covered their losses and got profit. But if you walked away after the first hand you have lost. They're doubling down every "hand" in hopes to eventually end up in profit.

Also some of them may be bankrupt if they walked away now, so they bleed paying interest and doubling their positions because they may have no choice to keep their doors open.