Not having to compete with professionals makes the game more fun for them.

Is this actually true? And how do we know this?

They still lose money but they "win" games more often and lose less money because they aren't losing as much to

Again, is this actually true? Do amateurs lose less money against each other when they are only playing other amateurs? If so, what is the reason?

With a higher rake the house may take $20 but without pros around the casuals may only lose a few dollars and maybe even end up a couple bucks ahead.

Is this true though? Someone has to lose in order for someone to win (or even break even for that matter), since everyone is paying even more rake to the house.

We know though as an actual fact that if the rake is higher, all players lose more money the longer the game continues.

It can be a solid theory if you take all statements as fact, but I think it's not