Buildings get torn down. Roof needs a replacement and the owner doesn't feel like it is worthwhile to redo the solar install for panels that only have 5 years of warranty left, or maybe they want to replace them with higher power models with a fresh warranty. There are any number of reasons why someone might need to offload otherwise functional solar panels.

In Ontario, there is a feed-in-tariff program for payment in exchange for renewable/green energy generation direct-to-grid. This program has contracts which expire. The microFIT program (under 10kW/hr solar capacity) has a bulk of contracts expire around the same short period of time.

There is not-yet a fully funded or thought-through method for extending contracts or providing better-than-dismantle options to contract owners that is/are accessible.