- the ease of apt-get install (inherited from debian)
- ubuntu LTS releases
I now use availability of apt-get instructions for an LTS as one of the measures of the maturity of a software package.
10 years ago, Debian may have had apt-get and stable but a lot of software setup docs were for building from source leading to possible compile issues and version conflicts for libraries.
Now, many setup docs are written as apt-get of binary packages for the last Ubuntu LTS.