I actually support your view but to play the other side of the argument for a bit: what you are suggesting is that the customer has to be an expert in tree health before they use a facility provided by the host. Do they also have to be an electrician before they trust the cooker wont electrocute them; or a heating expert to check the service condition of a heater so it doesn't leak CO and kill them in their sleep?
Electricity in a house is (usually!) installed by licensed electricians and inspected after installation, ditto gas and heating devices.
If you stay in someone else's apartment and it does not have a CO alarm and a stove that may or may not vent into the apartment then you should at a minimum sleep with a window open.
Tree-swings are not usually installed by licensed engineers, they are typically installed by people with a tree with a suitable profile, a rope and an old tire, any of which may fail at unpredictable times, but most likely when being used (and even more likely: when being used by an adult).
