I spent a long time trying to understand why DJB's software wasn't considered the gold standard and installed by default on all Linuxes and BSDs. I read lots about arrogance, but couldn't see any - I could only see a commitment to solid software.
Eventually the only theory I was left with was that perhaps the 'UNIX way' was something people didn't really understand, or didn't want to invest time into understanding. I'll draw a parallel with vi editor[s]: Those who invest time into understanding the vi philosophy are happy working with it and would rather not use anything else. Others think they (we - you might have guessed I'm a vi user) are somehow ultra geeky or hardcore. Maybe this is why there's a preference for server software with a shorter learning curve, too.
The thing I really didn't 'get' was that to me, djb's tools had no learning curve, because they work 'the UNIX way'. Perhaps this is why those who like[d] his software never made their voice heard enough, or did the work, to get them into mainstream distributions: They don't understand why others don't see that they're great.
There could be other reasons. For example: I gave up running my own mail server when I got sick of dealing with spam and couldn't find a decent web interface. I think squirrelmail was the best I could find at the time and gmail was so much better. Sorry, squirrelmail! Perhaps it was easier to integrate anti-spam software with other mail servers. Perhaps I never found out because I refused to use other mail servers, having seen all the security advisories. Maybe my refusal to consider 'insecure' software meant I was blind to the advantages of sendmail and postfix, rather than simply others being blind to the advantages of qmail.