Most gamblers know very well how to play certain games and don't really need any tutorials. How often does someone go to a physical casino, take out a $100 bill and go to a Blackjack table and just guess how to play the game? Almost never. They probably won't even want to risk betting $1 if they didn't know what they were doing. Hence this is the reason why many of the traffic to casinos usually just plays slots since its pretty much automatic as soon as you pull the lever. Either money comes out meaning you've won or nothing happens which means you lost.
You are partially right. A major portion of gamblers do know what they are doing thanks to their experience, but the posters above are discussing sports betting which could get complicated for newbies looking to bet for the first time in their life.
Terms like Handicap, Accumulator etc would confuse them which is why guides are essential(DarkoReborn already shared the links though).
But we cannot eliminate the fact that there are new born gamblers coming so I think he's request is reasonable since he want to know on how those games really works but it's stake management decision if they will implement that since his suggestion still helpful for newbies.