This issue is really what some people have already mentioned here, getting the aircraft back in case of delinquent payment.
I remember being at a GE party some years ago and talking to someone from ILFC about this very subject. They had had a 737 sitting in (I think) Krasnoyarsk for a couple of years that had been on a Russian registry. It had been impossible to get the aircraft out in one piece due to all sorts of hurdles being thrown up by various Russian agencies. So they were getting the aircraft back piece by piece. Disassembling it and bring out various components, a huge financial and administrative headache.
I remember him telling me that they would never register anything again on the Russian registry, after this whole ordeal.. Lease companies always need the option to get the aircraft back, be it to park it for better days or even part it out for components.