Backwards compatibility is a compelling reason to keep the two-spaces in the spec. Also, some people like their documents to look pretty, and the two spaces are invisible. I think it’s a matter of personal taste.
My own preference would be to get rid of the backslash-newline line break marker, in favor of reST-style line blocks:
| 200 Rose St.
| Salmon, WA 23433
That looks much less like a computer language.