[citation needed] - I would say most people will primarily use LAN services in private home/corporate networks. But I don't have a citation either.
It's different use cases. Maybe one needs the warning, the other one not. But putting the warning on everything and overload the user with them is not the right solution.
Using a self signed CA is a pity, because installing it on every phone, tablet, laptop, tv, pc, ... is cumbersome in a home network, and making all hosts public and depending on an external CA for local resources to not get scary warnings can not be the right solution either.
Sorry I don't have a citation here. But looking at my coworkers and family, none of them uses services in their home LAN. Most won't even know how to access the router.
On the other hand it's very common to use Wifi in public transport (at least here in London for the tube), airports, trains and hotels. Few people consider security when using these hotspots, making sure that SSL is enabled for all pages would be an improvement.
But do you use LAN services on that network? I think you will use that public hotspot to check facebook, hn, search something on google and stuff like that, not connect to some service in the local network of the hotspot.
- depending on an external service for your internal home stuff, or
- installing a self signed CA on every device you own
is not a solution.
Until we have something we can replace the status quo with, we should not deprecate it.
They don't have printers? They don't connect to a NAT router before their cable modem? They never tether their computer to their phone? Their DVR doesn't have an app to control it? None of them have their receiver connected to their iTunes library?
There's a clear divide that I see daily between households that understand their tech, and households that simply use whatever was set up for them. That divide seems to be growing wider, lately, too ...
For instance (to draw from your examples): 1) Most people either install the printer drivers from the manufacture's web site, or let Windows/OSX auto-discover and auto configure the printer with out a web browser. 2) Most users just use the wifi information provided by the cable/DSL provider when they installed the modem, use the WPS button, or install the app that came with their router rather than use a web browser to configure it. 3) Most users will not tether their computer to their phone. 4) Most don't install a DVR app on their phone. If they did, their phone probably communicates with their DVR via some intermediate cloud service. 5) If their receiver auto-connects to their itunes library, it probably won't complain about that itunes not having a public certificate either.