I think you'll find that with automotive models (i.e. nuvi's) that the vast majority of users stick them on their dash/windshield/etc and never connect them to a computer. They may connect the unit a computer to update the maps since most units popup a message after some time. In short BaseCamp, or any other software, is of no interest to these people.
I agree most nuvi users don't use BC but how would they know it is available. What would it hurt to give a description of BC in the 2013 Nuvi line manual and list it under features.
Motorcycle users (Zumo models) tend to plan their rides in advance so they do use BaseCamp or MapSource for that. The same applies to cyclists (Edge models).
True but I know cyclists and motorcyclists that have Garmin devices that don't use BC, I don't think they know it exists. I think RV's and driving vacationers plan almost as much as cyclists.
As for outdoor models (for which BaseCamp was first developed) I'm not sure. Personally I don't create routes for my hikes since Garmin's maps only have a few trails in my area and those are only partially accurate. Now I do record tracks and import those into BaseCamp (and MapSource) so I can view statistical data (trail grade, time, heartrate etc).
I like to create a track of the trail I am hiking in BC and check distance and elevation profile. GeoCaching is another outdoor activity that requires a GPS and BC does an excellent job of managing paperless geocaching. I think many GeoCachers use BC. It is simple and easy to use, works well and they don't have anything to whine about so they don't visit the forum much.
Now BaseCamp (and MapSource) are both free and "advanced" users (that is those that actually want to use their devices to their full potential) tend to use one or both. However the "average" user probably doesn't.
I think MapSource has always needed an advance user and getting BaseCamp maps on the computer is not for the novice. Prior to the Nuvi 2013 line, uploading a route that the GPS would follow, was impossible or requires an advance user depending on the Nuvi. However, with the Nuvi 2013 line, the novice user has the maps when the unit is plugged into the computer and dragging the route to the GPS will upload the route and the GPS will follow the BC route. Problem is I have never seen instructions with a GPS unit on using BC.
Well your 1 is exactly the same in Mapsource or indeed any mapping program, it can only route on maps it can see. Unlike some others though Basecamp can read the maps off your GPS.
As for 2 you just have to select the detail you want to send then drag and drop the selection into your GPS, exactly like dragging and dropping in Windows. It really couldn't be any easier.