Because it's not worth my volunteered time to remember all of the bugs fixed in the 17 versions of Perl released since Perl 5.8.8
1. There are no evidences that there are less bug in new version, see Re^2: Stop suggesting to upgrade perl
2. You don't have to remember all bugs
3. You don't have to answer questions
4. You don't have to answer questions which ask for support for older version of perl.
5. If certain perl version is business requirement, why answer with suggestion to drop this requirement?