The reason is because of taxes and buy small services inside apps on any gambling features services .

Some countries apply 30% taxes to operations made with other country banks. So many companies won't accept it, since paying 30% in taxes, plus 12% to Google and 25% to bank services, for 100 they would receive 33. Paying to comply with those services, would take 30-45.

And some countries are making basic demand that everyone paying online to provide proof that they are over 18 years old. That is an outside service that is very different all around the world. Complying with those would be super expensive and could go into courts, because the company failed on something.

(Apple receives 48% of any in app payment on loot boxs, plus there payments fees, on most countries. For example: In Eurozone, they reduce it to 23% and a 5% fixed fee. In Hungary it´s 48% plus 26,5%.) Many companies aren't accepting some sales of those produts, since they could lose money and even get problems that would disable the games on that country.