RealPlayer is used to display videos on the 3D cabinets. Media Player is mentioned in the docs, but I'm using the stock version that came with Windows 98SE and it works fine; it's used (presumably) for the startup videos and the sound effects.
In Howards defense, I'm sure very few people set out to say, "I'm going to create a FE app for the community". Most of them probably start out like my jukebox: they write them for their own caninets and their own environment, and release them to the public when people ask for them. I can tell you that my jukebox has no install application at all; it says "Unzip this and copy the DLL's to your WINDOWS/SYSTEM folder". Eventually, I may write a proper installer...
The bottom lne is, yes, all of the requirements should clearly be listed first, but the nature of these tools is that they're often designed for the author's fairly specialized environments, then released and maintained for free. I do wish Lazarus wouldn't need Shockwave or Real Player, because I would have absolutely no other reason to install them on a game cabinet....