If someone is sent a link to an internal AGO resource (dashboard, layer, app, etc.) and the user doesn't have permission they just get a page that says "you do not have permission to access the resource." Most BI tools (Tableau, PowerBi, etc.) also give the option to the user to request permission to the asset. As it stands, the user doesn't even know who owns the ArcGIS resource to even ask how to get permission - they have to ask the person who sent them the link, so might not even know the resource owner.
Is there any reason a capability has not been built in - I can't imagine we're the first one to bring this up, though I couldn't find a similar idea anyway.