I agree. That's why we use multiple cards. The purpose of this thread is actually to focus on cards which doesn't have the minimum spending requirements. There are in fact a few of these cards. POSB Everyday card, Maybank Family and Friends Card, Citibank Dividend Card (although you must spend at least $50 per transaction to hit the bonus rebate). Recently, I also started to use xtra saver debit card. It is 2% rebate regardless of where and the amount you spend.
Lastly, the Manhattan card used to be my favourite. It's 5% rebate. Say, if you spend $1000 this month and need another $2000 to reach the 5% rebate, you can make use of PayPal to hit that target. PayPal charges 3.4% + $0.50 which is lower than the 5% rebate you are getting. Say, if you have two Manhattan card (the platinum card and the world card) and your wife has two, then you can basically have 5% every month! Isn't that fantastic?