We published a blog post on this topic here. We find the practice a bit curious as well, but for whatever reason, the major rental companies have decided that longer rentals are more profitable and/or more efficient and they all have begun instituting these sorts of policies of late.

It got so bad that we even had to build an internal tool to try extending the return date to find the minimum rental length that would return availability because so many of our customer requests were just returning no availability.

We wish we had more insight into this but it's very real and very prevalent.