UK online casinos operate under strict rules set by the UK Gambling Commission...

https://businessmodelanalyst.com/the-uk-online-casino-business-model-revenue-streams-regulation-and-competitive-dynamics/

UK online casinos operate under strict rules set by the UK Gambling Commission to ensure fairness and player protection. They often offer games with a minimum 96% return to player (RTP), meaning most bets are returned over time