Unless you are in some trivial startup domain, real domains (TM) have almost fractal-level complexities if you dig deep enough, corner cases, sometimes illogical rules etc.

The "why" is still very much needed since it can have 10 different and even conflicting reasons, and putting it in the code in appropriate amount shows certain type of professional maturity and also emotional intelligence/empathy towards rest of the team.

I mean, somebody has to be extremely junior to never experience trying to grok somebody's else old non-trivial code in situation when you need to deliver fix/change on it now. And its fairly trivial to write very complex code even in few lines, which some smart inexperienced juniors (even older, but total skill-wise still juniors) produce as some sort of intellectual game out of boredom.