TheRock wrote:

Why is that...does it have something to do with "time to live" for the
message ?



No.It's a storage and bandwidth issue for server admins mostly. Groups
that are not text only always have the word "binary" in their name.
These groups have messages that are much larger (byte wise) than the
text only groups. This naming convention allows news admins to avoid the
groups with huge messages if their server is on a slow link.