for what reason, how come, to what end, for what purpose, to what purpose, wherefore(literary, archaic), why ever, whyever, why on earth, why the hell(potentially offensive, slang), why the fuck(vulgar, offensive, slang)
Sense: Conjunction: the reason why
the reason, the reason that, the reason why, the reason for, wherefore(literary archaic)
Sense: Noun: reason - plural, often preceded by 'the'
the wherefores, the why and wherefore, the reason why, reason, pretext, explanation, motive