[1] https://taginfo.openstreetmap.org/keys/contact:facebook [2] https://taginfo.openstreetmap.org/keys/contact:instagram
> Determine if any of the search results represent the official website for your place. Do NOT use search results for social media profiles, review sites, or other business aggregators. When in doubt, don’t use it.
This zero-option style of phrasing doesn't leave any room for interpretation.
It's also the place that will allow you to inform your patrons when big tech deletes your heavily invested in social media account for some reason.
Not having a normal website means that potential customers who search for you get hit by login-walls for Instagram and Facebook if they're not on it, or 'you need an app for this' with crap like TikTok. It also makes my (volunteer) job of mapping the area around me harder, because I'm most certainly not going to bother to enter any additional info about your business if I have to go to Instagram or Facebook (and in the OpenStreetMap community I'm not alone in that).
While all of then problems you list are real, small restaurant owners don’t have the time or skills to run a website, having a social media and listing on the maps apps is enough.