For the same reason that I write my modules to deliberately support Perl 5.0.0 and higher - to increase the usability of my work. The majority of CPAN modules are written with "use warnings;" and "our" ... should I follow that if I don't have to?
Being right, does not endow the right to be rude; politeness costs nothing.
Being unknowing, is not the same as being stupid.
Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.