Wha?
Nulls are treated as part of the word by Text::Wrap; and a sequence of nulls
will not be broken in the middle unless the sequence is longer than the desired
width of the output. If Text::Wrap broke a string between two nulls subsequent
line wrappings would be off.
The last point is moot, since the nulls get stripped.
But other reasons for the initial choice of null is that it doesn't
usually show on a display and null is not a member of a figfont.