No rhyme or reason means no sense or pattern to it whatsoever. There is no rhyme or reason to it.
It complains about a system rather than a decision, since one decision can simply be wrong. To say there is no rhyme or reason is stronger than saying something is unfair.
1phraseno rhyme or reasonNo sense or pattern to it whatsoever.
“There was no rhyme or reason to which streets were cleared first.”
no rhyme or reason is a phrase.
Also accepted in games: neither rhyme nor reason
Practised in Idioms