very few people ever bother to change them unless a specific, user visible problem is occuring
due to the first point, non-defaults receive little or no testing, and are highly likely to be broken, and stay broken because the catch 22 of nobody cares so its broken, and because its broken nobody cares.
Off by default is very much the status of mitigation technologies in FreeBSD atm, its a shame that the author did not touch on this as its one area OpenBSD is miles ahead of FreeBSD in particular (mitigations on by default, breakage exposed and fixed due to it, they remain mostly unusable on FreeBSD due to them).