> Doesn’t Epic charge a 5% royalty for any games developed on Unreal Engine regardless of where or how the money is collected or what app store it’s installed from?

"Royalty". It's common to charge a royalty when allowing someone to distribute your copyrighted property.

> Why can’t Apple collect fees for any apps that are built on their software AND hardware?

Because that's not a royalty - you aren't distributing Apple's copyrighted property when you send someone an iPhone application.[1]

When you send someone your game built on Unreal Engine, you are sending them Epic's copyrighted property.[2]

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[1] If people could side-load iPhone apps, that is. I don't believe that they can.

[2] If you sell someone code to your game and tell them to to download Unreal Engine, then compile and/or link it against Unreal Engine themselves, then sure, Epic won't get a dime. But your customer might still have to pay for that, depending on whether Epic makes single-user no-sale licenses free (I believe they do).