Because the bad ones are removed. Happened to one of mine. Doctor didn't want to care on Christmas because I did not have an Überweisung. instead i wanted to pay 10 euros (which in fact was legal then). Jameda just deleted it without notice.
In times of corona measures there have been a lot of ratings made by angry people. Some where like "0 stars the doctor is doing vaccines". So this and the felt popularity decline of such portals (like everywhere) screams for adjustment.