In general, I trust the folks running the distro more than the folks writing the software in the first place. If nothing else, they provide/enforce a second pair of eyes to sanity check things before they get shipped.
The distro also gets to choose a graph of known-good non-conflicting dependencies each time they cut a stable release. If the original author is catering to users who don’t use package databases, he won’t know what they may have available.