@Fred13. While I'm sure that there are some abuses by guests using this feature, the problem is that many hosts, in the situations I mentioned before, won't cancel and ask the guests to cancel. This is the only way a guest can request that the host cancel or re-confirm that the host will honor the reservation as it was booked and confirmed.
In situations where a host has failed to keep thier listings updated for pricing, availability, minimum stay requirements, it should be the host who cancels, not the guest. Obviously the host should keep these reservations and not cancel since the penalties involved would preclude other bookings.
So lets say I book a place over Super Bowl weekend in Minnesota and later the host says "I forgot that weekend was Super Bowl and my rate is actually three times higher than the rate you booked. I will send you an alteration to the price for you to accept". I selected that listing because the rate advertised at the time suited my budget and was very attractive. I've already paid for the reservation and now I don't know what to do since I do not want to pay more. I need the host to either re-confirm they will honor my reservation as booked or cancel so I can get a full refund and look for another place to stay.
I would grant you that the wording on the notice should be revised so that hosts don't believe that they are doing a guest a favor by cancelling. Perhaps the wording should be "Clare requests that you confirm her reservation as originally booked and if you are not able to host her stay, please cancel."
If you are able to get an explanation from Airbnb as to why this feature is available, I would be fascinated to know the answer. Keep me posted!