The omniscient Norman seems to have nailed me:
Judging by the manuals, Research did it first. In
every manual from
1/e to 6/e, the entry for ls(I) has this description for the -a option:
list all entries; usually those beginning with
"." are suppressed
I suspect that in v7 (where .thing was indeed listed by default)
we decided that since .thing was a real file in the
directory it was better to list it instead of hiding it
by default. (Seeing . and .. seemed seldom interesting,
however).
I was solely (and much more recently) responsible for the lack
of subject header in my earlier reply.
Dennis