You are trying to look at this from a common sense or logical perspective........or worse as an engineer (no offense)… none of which really works when looking at potential legal liability. Many law suits do not make sense and are sure not logical.
From the perspective of a binding manufacturer, bindings are only to be mounted by a mechanic that is certified by that particular manufacturer. Once mounted, the mechanic is to set the release settings in accordance with the accepted industry standard (which in the ski industry is the German DIN standard), and based on the information provided by each individual customer (i.e. Age, weight height and skiing ability etc.) and then record the settings on the shop ticket. When a customer picks up his skis, the shop should explain how the binding operates, show the customer the DIN setting used based on the information provided, and have the customer sign the shop ticket verifying the binding settings at the time the skis were picked up. From a legal perspective, if all of these items are performed correctly, then the shop complied with the accepted industry standard and there should be no negligence on the part of the shop and/or mechanic. Additionally, the manufacturer will indemnify the shop and mechanic should someone file a law suit alleging the plaintiff’s injuries were cause by the bindings being negligently installed or adjusted.
Of course in our litigious society none of this will stop someone from bringing a law suit, but in bringing an action for negligence, the plaintiff would have the burden of proving the shop and/or mechanic was negligent and that they deviated from the accepted industry standard. Should a suit arise and the shop had properly adjusted the bindings based on the information provided, documented the settings and had the individual sign the shop ticket acknowledging the DIN settings, the signed shop ticket acknowledging the DIN settings is evidence that the work was done in compliance with accepted industry standards and creates a much greater burden on a plaintiff to prove negligence on the part of the shop/mechanic. This is over simplified and defending a negligence action is not this simple, if everything is done properly, hopefully most personal injury attorneys will see there is no basis and not file suit. (Given the cost of defense it is always cheaper to prevent the action from being filed in the first place)
None of this prevents an individual from mounting and adjusting their own skis, and many people do change the DIN settings on their bindings, there are no laws against this, but in doing so, an individual assumes whatever risk is involved upon themselves. Unfortunately, this is why it makes it that much more important for a mechanic to document the settings and get the ticket signed.
This is also why ski patrols are instructed to records binding settings, take statements from witnesses and if possible take photographs of the injury scene and binding settings…all of which can be important to whoever is defending a law suit alleging negligence against a shop or binding manufacturer. (Not to mention a suit against the area)
In regards to an automobile repair shop, it involves completely different legal duties, since the basis for keeping customers out of the work area is based more on premise liability and not the work itself performed by the mechanic.
All of this being said, a very wise Judge once told me that regardless of the law and/or facts of a case, the only thing limiting a plaintiff in any given law suit is the imagination of his attorney…and believe me, there are some very imaginative trial lawyers out