Like others have said, any industry has the purpose of extracting money from the customers.

The original poster has not expressed this correctly, but I assume that the intention was to say that the gambling industry is different from all other industries, not because it extracts money like any other industry, but because it does not return a product or service for that money.

The porn industry is no different from any other entertainment industry and it provides a service for money.

Gambling does not really provide any service, it just exploits the hope of the gamblers that they might gain something by gambling, which at least on average, never happens.

I do not think that one can call the stimulation of this hope of gaining as entertainment. There are some gamblers for which gambling is really entertainment, i.e. they are rich and they do not seriously expect to gain anything, but the majority of the gamblers do not do this to be entertained but because of the irrational hope of gaining enough to solve all their problems.