Why prevent the mailing list from being indexed?

[Stephane Chazelas <stephane.chazelas@xxxxxxxxx>]

I was surprised when a google search on the zsh mailing list
archives turned up nothing when I knew it should (site:zsh.org
ZSH_XTRACEFD) and then saw:

https://www.zsh.org/robots.txt

User-agent: *
Disallow: /cgi-bin/
Disallow: /mla/zsh-announce/
Disallow: /mla/zsh-users/
Disallow: /mla/zsh-workers/
Disallow: /pub/old/

Why?

Having google/duckduckgo searches return results from there
would be very useful, especially considering that the mailing
list is also used as an issue tracker and to some extent as a
changelog.

I know (well, I just discovered) it can be queried with
https://www.zsh.org/cgi-bin/mla/wilma_glimpse/workers?query=ZSH_XTRACEFD
but you have to know it's there and look explicitely in the ml
as opposed to generally on the web.

-- 
Stephane