This is superficially true but I think ignores how usable sam is. The rationalized command language, the fact that you can see what you're doing, unlimited undo even across files (even across file I/O), and the ability to go to the file in question and just type make it a much more satisfying experience to do large amounts of development with than ed is.
Yes. Vi is also not too dissimilar to ed, but much more useful. (Also NetHack is quite similar to Vi, and much more useful and fun in turn.)
The standard editor!
I want a editor! Not a samitor or an emacsitor or a viditor!