Mostly his disregard for packaging conventions and unwillingness to acomodate them. The code is usually A grade, but the odd use of the filesystem, runtime configs, daemons etc. means it will never get into any mainstream distro without heavy patching.
There's a reason why libsodium's tag line is "P(ortable|ackageable) NaCl-based crypto library".
The word of distros/packagers isn't gospel, but it counts for a lot, considering that (for better or worse) most people won't even think about using something not available as a package.
I've been doing "apt-get install daemontools daemontools-run" since forever on Ubuntu; it might take a little longer to get into the repositories, but it does get into mainstream distros with almost no patching -- comparable, IIRC, to packages of similar size and complexity that do not have an upstream debian packaging.
There's a reason why libsodium's tag line is "P(ortable|ackageable) NaCl-based crypto library".
The word of distros/packagers isn't gospel, but it counts for a lot, considering that (for better or worse) most people won't even think about using something not available as a package.