Senders often want to _encourage_ followups and _discourage_ replies.
That doesn't mean senders want to _break_ the reply mechanism.
Mail doesn't have "followups", it has replies.
People keep falling back on that (correct) formal statement. However, in
practice, users don't perceive much (any?) difference between mail and
news. They use the same agents to process all kinds of messages, which
sometimes have come by mail, and sometimes have come by news. I'm sure
that in many users' minds a newsgroup is just another kind of mailing
list.
The conclusion seems fairly obvious...
perhaps to you. I can find two fairly obvious, but contradictory,
conclusions:
1. people are confused by the apparent similarity, so we'd serve people
better by trying to make the differences more apparent
2. people want to treat the two as identical, so we should try to make
them work as similarly as possible
actually I don't believe that "users don't perceive much (any?) difference
between mail and news." people are very good at managing differences in
social contexts, even if they don't take the time to analyze them or to
express those differences in words. people figure out very quickly that
there are differences in privacy, style, and other social norms between
the two media. they may get annoyed when either system doesn't support
the functionality that they need - but this isn't an argument for making
the two systems the same.