Well, if your friend lives close to the edge of your range, it might make a lot of sense to charge there. And if I'd installed a permanent L2 charger at home, I'd leave the cable that came with the car in the car, I know my car has a spot to store it, most others do too. And my friends who live far enough away for it to matter have things like "get an electric car" on their list of things to do as soon as they can afford it, so at some point I wouldn't even need my own cable. So yeah, charging at a friend's place is something I'd do.
And yeah, when I get a pure electric car, L3 availability is going to be important, not so much for daily driving, but for road trips. And if I had a pure electric, I'd definitely install the L2 at home, you're not going to get 300 miles of charge overnight on 120V, and that range is pretty much what it's going to take for me to go pure electric instead of plug in hybrid. I'll never need it most days, but if I'm doing electric only I've gotta cover the outliers. 300 miles should do it, it'll cover days when I've got to travel to surrounding states, and with enough available L3 chargers, I'd be able to do most road trips.