Roaming tariffs: why do public chargers still cost double?

I’ve been using a mix of networks for a trip across Belgium and Germany, and the price difference is staggering. My home wallbox costs €0.25/kWh, but on the same day I paid €0.79 on a roaming charger through my provider’s app. Even direct card payments were around €0.55. Why is the gap still so wide in the EU? I thought roaming regulation was supposed to help, but it seems like every network has its own pricing silo. How do you all pick which apps to rely on? Any tricks for finding fair per-kWh rates without subscribing to ten different services? Curious to hear what others are seeing in their countries.