In Poland fees are capped at 0.3% for credit card, 0.2% for debit per EU. Which is why generally in the EU you don't have the insanity with credit card loyalty programs.
Also, some of us have actual lives to live and not obsess over such details, life is way too short and has much more to offer than bean counting accounting.
And yes so far I’ve only seen childless people do this optimization. It seems likely that when life gets busier, a person wouldn’t find time to do this optimization.