Except that your reasons which you listed are actually incorrect.
SMF does not have an archaic database structure.
SMF does not have missing features. It has a very SIMPLE feature set for INTENTIONAL reasons -- and then has mods for almost any additional feature that is desired.
SMF has perfectly fine API and SSI support (although such is not needed on this site, so that is not actually a consideration.)
SMF 2.0 (default) theme is somewhat limited in the mobile/responsive design. True... Although there is a mod which makes the Curve theme somewhat responsive... However, this site uses a fully responsive theme -- which means that your comment on mobile support is just plain wrong.
and... as already stated... SMF's support is actually very good. (heck, this site has the PM for SMF personally providing support!)
finally... while phpBB may have a wider install base - that does not make it "better". SMF has several features that phpBB is missing (like the package manager, which is huge) and SMF definitely has a wider install base than myBB (although, once again, more != better) (and vB is paid, so that should not enter into consideration - apples to pears)
In short -- there actually is not really any bias in my defense. All of the above statements are factual... and while you can have a disagreeing opinion, your opinion doesn't change the facts.