That's because it was conspicuously missing as an answer from our respondents.

We got exactly four responses for Bazaar and one for Fossil out of nearly a thousand. They are just tiny in comparison to the rest.

I keep seeing posts about large organisations (off the top of my head, python and mozilla) consider bzr, and then discount it.

This mostly seems to be because of its performance.

Having used git and bzr extensively (and a bit of mercurial), I've found it's performance to be perfectly fine for general use on reasonably sized projects, and the ease-of-use to be far superior. Figuring out how to get Bazaar to do something you haven't done before is much easier than trying to track down a Git feature. Although I will admit that Git is improving in this regard, while Bazaar continues to improve it's performance and focus on interoperability.

Anyway, in summary: I really don't get why more people aren't using Bazaar.

I'm not so sure. All but one of the Bazaar users I know uses it only because Canonical and/or GNU* require it.

* Emacs uses Bazaar for "branding" reasons IIRC.

There's also ClearCase, which I believe is popular in Big Iron Enterprise shops.

If the survey was done properly, then 'other' consists of lots of different things and bzr is just a small chunk of it not worth dealing with separately.

If the survey was done badly, with an 'other' option with no way to write in what you use, then potentially all of the 'other' block could be bzr. It would just be left out by the survey writer not having heard of it.

Don't forget Fossil