When Marriott acquired Starwood and merged the loyalty programs, as much changed with their credit cards as with the loyalty program itself.
Chase’s Marriott cards used to earn 1 point per dollar. Starwood’s Amex cards earned 1 Starwood point per dollar. Marriott themselves declared 1 SPG point worth 3 Marriott points. In other words, the Amex cards were 3 times as rewarding for spending.