A card that earns the same modest rate on everything has a quiet appeal: no categories to track, no juggling, no decision at the register. For a meaningful share of people, that simplicity is worth more than chasing a slightly higher rate. The honest question is which kind of person you are.
The case for one flat-rate card
A flat-rate card removes effort entirely. You earn a steady return on every purchase without thought, and there is real value in a system you will actually stick to. The best strategy is the one you follow, not the one that looks optimal on paper.
What you give up
The trade-off is the extra earning you would get from bonus categories on spending you do heavily — the gap described in "The opportunity cost of putting spend on the wrong card." For some, that forgone value is small; for others, it adds up.
Who is best served by simplicity
Someone with spending spread evenly across many small categories, or who simply will not maintain a multi-card routine, is often well served by one flat-rate card. Simplicity is not a compromise for this person; it is the right answer.
Who should reach further
Someone who spends heavily in a clear category may leave real value behind with a flat rate, and could benefit from pairing cards, as "How category bonuses work" describes. The heavier and more concentrated your spending, the stronger that case becomes.
A sensible middle ground
Many people land well with a flat-rate card as a base and one category card for their largest spending area — the two-card idea from "Building a two-card system." It captures most of the value while keeping the routine light.
A flat-rate card is not a lesser choice; for many people it is the wiser one. Match the effort to the value, and keep what you will actually use.
