I guess I just take issue with saying the "general case" usage of strings does not have to avoid copies. That is how we generally wind up with slow, bloated software.
I don't think most software is particularly slow or bloated. It's been quite some time since I thought to myself, "gee, this software could do with being a lot faster", outside of games and video transcoders (and perhaps iTunes on Windows). On the other hand, a lot of software has buffer overflow vulnerabilities; I see a lot of crashes when input data is fuzzed or corrupted slightly.