you miss the point — the banks don’t own the debt anymore.
To add to the mess, it’s not entirely clear who does own the mortgage. The loans were sliced, diced, cubed, quartered, etc, sold, and resold. Deutsch Bank tried to foreclose on some properties in Ohio, and a judge ruled that while DB owns the asset-backed securities (aka “ass-paper”), nobody could come up with the mortgage paperwork itself. Can’t make this stuff up.