Refunds came about because of EU laws. Those flash sales would have resulted in a bunch of refunds so they stopped doing them at the same time. They actively encouraged (and still do) people to refund & rebuy for cheaper at any time whether any steam sale is involved or not as long as within the refund terms.
Personally, I only miss the mini games they had during those sales but I hated the flash sales themselves. Had to waste time researching when the games wanted were going to be the cheapest during the flash sale. Then had to hope it was during some free point of the day, notification/alarm worked, or that didn’t forget to create the notification/alarm. Then had to hope the store wasn’t overloaded because everyone else was also trying to get in on time limited sales.