The U.S. representatives conducted hearings in the move from one flight attendant per 50 seats to one flight attendant per 50 passengers.
To be clear on the origin of the rule, the rule originated in 1971. Australia had one flight attendant per 36 passengers. The U.S. at that time had one flight attendant per 44 seats. Canada took the middle: one flight attendant per 40 passengers. Then the U.S. moved from one flight attendant per 44 seats to one flight attendant per 50 seats. The U.S. NTSB said it is unproven.
The airlines then said they'd like to go to one flight attendant per 50 passengers, to give them the flexibility and even fewer flight attendants, because they would be able, then, to staff to load as well.
The U.S. House of Representatives stepped in, convened a full day of televised public hearings, and rejected it based on the evidence presented.